Q: What is meant by an I-V characteristic?
A: An I-V characteristic is a graph that shows how the current (I) flowing through a component changes as the potential difference (V) across it is increased.
Q: What does an I-V graph show?
A: An I-V graph shows the relationship between current through a component and the potential difference across it.
Q: What is the aim of the I-V characteristics required practical?
A: The aim is to investigate the relationship between current and potential difference for different components, specifically a resistor, bulb (filament lamp), and diode.
Q: What must be measured and observed in this practical?
A: You must measure and observe both the current and the potential difference for each component.
Q: What type of circuit is used in this practical?
A: A direct current (dc) series circuit is used.
Q: What apparatus is used to measure current in this experiment?
A: An ammeter is used, and it is connected in series with the component.
Q: What apparatus is used to measure potential difference in this experiment?
A: A voltmeter is used, and it is connected in parallel across the component.
Q: What is the role of the variable resistor in the circuit?
A: The variable resistor is used to control and vary the current flowing through the circuit and the potential difference across the component.
Q: What components are typically investigated in this practical?
A: A fixed resistor, a filament lamp (bulb), and a diode.
General Method
Q: How is the circuit set up at the start of the experiment?
A: The circuit is connected with a power supply, a variable resistor, an ammeter in series, a voltmeter in parallel, and the component being tested.
Q: What must be ensured before starting measurements?
A: The power supply should be set to zero at the start.
Q: How are readings taken during the experiment?
A: Readings of current from the ammeter and potential difference from the voltmeter are recorded.
Q: How is the potential difference changed during the experiment?
A: The variable resistor is adjusted to alter the current and potential difference.
Q: What is done after adjusting the variable resistor?
A: New readings from the ammeter and voltmeter are recorded.
Q: How many readings should be taken and why?
A: Multiple readings should be taken to improve accuracy and allow calculation of an average.
Q: How are averages used in this experiment?
A: Each reading can be repeated (e.g. twice more) and an average potential difference is calculated for each current.
Q: How is the relationship between current and potential difference fully tested?
A: The power supply connections are reversed to reverse the direction of current and measurements are repeated.
Q: What is done after all readings are collected?
A: A graph of current against potential difference is plotted.
Q: Why are separate graphs plotted for each component?
A: Because each component has a different I-V characteristic and must be analysed individually.
Method for Diode (Specific)
Q: How does the diode method differ from the general method?
A: A protective resistor (between 100 Ω and 500 Ω) is used, and a milliammeter may be used due to smaller currents.
Q: What is the first step when testing a diode?
A: Set the variable resistor to give the lowest potential difference and record readings.
Q: How is the potential difference increased for a diode?
A: The variable resistor is adjusted to increase the potential difference in small steps, typically 0.2 V.
Q: What is done after each increase in potential difference for a diode?
A: New readings from the voltmeter and milliammeter are recorded.
Q: How is the diode tested in both directions?
A: The power supply connections are reversed and the process is repeated.
Q: What is done after collecting diode readings?
A: A graph of current against potential difference is plotted.
Types of I-V Characteristics
Q: What is a linear component in terms of I-V characteristics?
A: A linear component has a straight-line I-V graph, showing current is directly proportional to potential difference.
Q: Give an example of a linear component.
A: A fixed resistor.
Q: What is meant by “directly proportional” in this context?
A: It means that as potential difference increases, current increases at a constant rate.
Q: What is a non-linear component?
A: A non-linear component has a curved I-V graph, meaning current is not proportional to potential difference.
Q: Give examples of non-linear components.
A: A filament lamp and a diode.
Graph Analysis: Ohmic Conductor
Q: What is an ohmic conductor?
A: An ohmic conductor is a component (like a resistor at constant temperature) where current is directly proportional to potential difference.
Q: What does the I-V graph of an ohmic conductor look like?
A: A straight line through the origin.
Q: Under what condition does a resistor behave as an ohmic conductor?
A: When its temperature remains constant.
Graph Analysis: Filament Lamp
Q: What happens to the I-V graph of a filament lamp as current increases?
A: The graph curves and becomes less steep (shallower).
Q: Why does the filament lamp graph curve?
A: Because as current increases, the filament heats up, increasing its resistance.
Q: How does increased temperature affect resistance in a filament lamp?
A: Resistance increases as temperature increases.
Q: How does increased resistance affect current flow?
A: Less current flows per unit potential difference, causing the graph to flatten.
Graph Analysis: Diode
Q: How does current behave in a diode?
A: Current flows easily in one direction but very little flows in the opposite direction.
Q: What does the I-V graph of a diode show?
A: A sharp increase in current in the forward direction and almost no current in the reverse direction.
Q: What is the resistance of a diode in the reverse direction?
A: Very high resistance.
Calculations
Q: How can resistance be calculated from an I-V graph?
A: Using the equation R = V / I at any point on the graph.
Q: Which formula links potential difference, current, and resistance?
A: V = IR.
Hazards and Safety
Q: What is a key hazard in this practical?
A: Heating of the resistance wire.
Q: What is the possible consequence of this hazard?
A: Burns to the skin.
Q: How can this risk be controlled?
A: Avoid touching the resistance wire while the circuit is connected and allow time for it to cool before handling.
Source 1: Required Practical: I-V Graphs:
This practical investigates the I-V CHARACTERISTICS of different components.
I-V characteristics are GRAPHS that show how the CURRENT (I) through a component changes with the POTENTIAL DIFFERENCE (V) applied to it (also know as I-V Graphs).
TYPES OF I-V CHARACTERISTICS:
LINEAR COMPONENTS (like a fixed resistor) show a STRAIGHT LINE on the graph, indicating that current and potential difference are DIRECTLY PROPORTIONAL.
NON-LINEAR COMPONENTS (like a filament lamp or a diode) show a CURVED LINE, meaning the relationship between current and potential difference is NOT proportional.
METHOD: Build the TEST CIRCUIT with a VARIABLE RESISTOR to CONTROL current, an AMMETER in series to measure CURRENT, a VOLTMETER in parallel to measure POTENTIAL DIFFERENCE and the COMPONENT being tested.
Change the variable resistor to alter the CURRENT flowing through and the POTENTIAL DIFFERENCE across the component.
Record READINGS from both the ammeter and voltmeter as you adjust the variable resistor. Take multiple readings to ensure accuracy and calculate an average.
SWAP the connections to the battery to reverse the current’s direction. This checks the component’s behaviour in both directions.
PLOT a graph of current against voltage to visualise the component’s I-V characteristics.
GRAPH ANALYSIS:
The graph you get will be different depending on the component being tested: The graph for an OHMIC CONDUCTOR (like a resistor) will be a straight line.
The graph for a FILAMENT LAMP will start to curve as the current increases due to the filament heating up.
The graph for a DIODE will show current flow in one direction and very little in the opposite direction. //////////// Source 2: Investigating the I-V characteristics of electrical components: Required practical - investigate I-V graphs:
There are different ways to investigate the relationship between current and potential difference . In this practical activity, it is important to:
- measure and observe current and potential difference
- use appropriate apparatus and methods to measure current and potential difference for a resistor, bulb and diode || Aim of the experiment: To investigate the relationship between current and potential difference for a resistor, bulb and diode.
Method:
1. Connect the circuit as shown in the first diagram.
2. Ensure that the power supply is set to zero at the start.
3. Record the reading on the voltmeter and ammeter .
4. Use the variable resistor to alter the potential difference.
5. Record the new readings on the voltmeter and ammeter.
6. Repeat steps three to four, each time increasing the potential difference.
7. Reverse the power supply connections and repeat steps two to six.
8. Plot a graph of current against potential difference for each component 1.
9. Repeat the experiment but replace the fixed resistor with a bulb. || There is a slightly different method for this experiment for DIODES: Connect the circuit as shown in the diagram having chosen a suitable protective resistor (between 100 Ω and 500 Ω).
Set the variable resistor to give the lowest potential difference and record the readings on the voltmeter and milliammeter.
Alter the variable resistor to increase the potential difference by 0.2 V.
Record the new readings on the voltmeter and milliammeter.
Repeat steps three to four, each time increasing the current slightly.
Reverse the power supply connections and repeat steps two to six.
Plot a graph of current against potential difference for the diode. || Hazards and control measures: Heating of the resistance wire as a significant hazard, which can lead to the consequence of burns to the skin. To manage this risk, the recommended control measures are to avoid touching the resistance wire while the circuits are connected and to allow it sufficient time to cool before handling. //////////// Source 3: Three Very Important I-V Characteristics: PRACTICAL:
Note: This type of circuit uses direct current (dc) and is a series circuit.
The term ‘I-V characteristic’ refers to a graph which shows how the current (I) flowing through a component changes as the potential difference (V) across it is increased.
Linear components have an I-V characteristic that’s a straight line (e.g. a fixed resistor).
Non-linear components have a curved I-V characteristic (e.g. a filament lamp or a diode).
You can do this experiment to find a component’s I-V characteristic:
Set up the test circuit shown on the right.
Begin to vary the variable resistor. This alters the current flowing through the circuit and the potential difference across the component.
Take several pairs of readings from the ammeter and voltmeter to see how the potential difference across the component varies as the current changes. Repeat each reading twice more to get an average pd at each current.
Swap over the wires connected to the battery, so the direction of the current is reversed.
Plot a graph of current against voltage for the component.
The I-V characteristics you get for an ohmic conductor, filament lamp and diode should look like this:
Ohmic Conductor:
(e.g. resistor at constant temperature)
The current through an ohmic conductor (at constant temperature) is directly proportional to potential difference so you get a straight line.
Filament Lamp:
As the current increases, the temperature of the filament increases, so the resistance increases. This means less current can flow per unit pd, so the graph gets shallower — hence the curve.
Diode:
Current will only flow through a diode in one direction, as shown. The diode has very high resistance in the reverse direction.
[Since V = IR, you can calculate the resistance at any point on the I-V characteristic by calculating R = V / I.]
Q: What is meant by an I-V characteristic?
A: An I-V characteristic is a graph that shows how the current (I) flowing through a component changes as the potential difference (V) across it is increased.
Q: What does an I-V graph show?
A: An I-V graph shows the relationship between current through a component and the potential difference across it.
Q: What is the aim of the I-V characteristics required practical?
A: The aim is to investigate the relationship between current and potential difference for different components
specifically a resistor
Q: What must be measured and observed in this practical?
A: You must measure and observe both the current and the potential difference for each component.
Q: What type of circuit is used in this practical?
A: A direct current (dc) series circuit is used.
Q: What apparatus is used to measure current in this experiment?
A: An ammeter is used
and it is connected in series with the component.
Q: What apparatus is used to measure potential difference in this experiment?
A: A voltmeter is used
and it is connected in parallel across the component.
Q: What is the role of the variable resistor in the circuit?
A: The variable resistor is used to control and vary the current flowing through the circuit and the potential difference across the component.
Q: What components are typically investigated in this practical?
A: A fixed resistor
a filament lamp (bulb)
General Method
Q: How is the circuit set up at the start of the experiment?
A: The circuit is connected with a power supply
a variable resistor
Q: What must be ensured before starting measurements?
A: The power supply should be set to zero at the start.
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Energy Stores and Transfers, Open and Closed Systems36
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Examples of Energy Transfers, Energy Flow Diagrams13
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Calculation of Energy Changes, Conservation of Energy11
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Energy Dissipation, Reducing Unwated Energy Transfers in the Home13
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Conduction and Convection112
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Specific Heat Capacity, Intro to Thermal Conductivity22
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Required Practical: Specific Heat Capacity20
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Power124
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Required Practical: Investigating Insulation121
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Efficiency108
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Types of Energy Resources290
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Trends and Uses of Energy Resources, Energy for Transport and Heating246
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Charge and Current82
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Current, Potential Difference & Resistance58
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Required Practical: Investigating Resistance89
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Resistors and I-V Graphs132
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Required Practical: I-V Graphs99
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Series and Parallel Circuits55
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Direct and Alternating Current31
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Mains Electricity78
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Electrical Power25
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Electrical Energy Transfers and Power Ratings71
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The National Grid84
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Static Electricity and Sparks77
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Electric Fields and Sparks75
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Density - Intro13
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Required Practical: Density17
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States of Matter36
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Internal Energy35
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Specific Latent Heat, Heating & Cooling Graphs (and recap of Internal Energy)36
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Particle Motion in Gases, Gas Pressure & Temp, Boyle's Law, Work Done on Gases41
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Atomic Structure, Radioactive Decay, Types of Radiation, Intro to G-M Tube75
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Nuclear Equations, Half Life, Contamination, Irradiation, Peer Reviewing79
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Nuclear Fission and Fusion97
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Scalars and Vectors24
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Contact and Non-Contact Forces71
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Gravity, Weight & Centre of Mass97
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Resultant Forces, Scale Drawings, & Components of a Force113
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Work Done and Its Energy Transfers53
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Forces and Elasticity112
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Required Practical: Force and Extension118
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Moments, Levers and Gears101
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Pressure in Fluids118
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Upthrust and Atmospheric Pressure67
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Distance and Displacement17
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Speed and Velocity25
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Distance-Time Graphs24
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Acceleration106
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Velocity-Time Graphs61
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Terminal Velocity121
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Newton's First Law and Inertia61
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Newton's Second Law and Inertial Mass51
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Newton's Third Law73
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Required Practical: Force, Mass and Acceleration137
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Stopping Distance and How Braking Works131
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Momentum and Changes in Momentum104
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Vehicle Safety Features40
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Transverse & Longitudinal Waves36
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Wave Period & Speed, Measuring the Speed of Sound in Air23
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Required Practical: Measuring Waves in a Ripple Tank19
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Required Practical: Measuring Waves on a String9
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Sound Waves and Human Hearing101
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Using Ultrasound for Imaging and Detection70
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Using Seismic Waves for Exploration81
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Intro to Electromagnetic Waves, Intro to Visible Light92
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Uses of Radio Waves91
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Uses of Microwaves25
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Uses of Infrared Radiation33
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Uses of Visible Light21
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Uses of Ultraviolet Radiation25
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Uses of X-Rays and Gamma Rays27
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Dangers of Electromagnetic Waves63
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Visible Light and Colour Filters137
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Required Practical: Investigating Infrared Radiation75
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Reflection and Refraction114
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Specular and Diffuse Reflection61
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Required Practical: Reflection and Refraction119
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Lenses and Ray Diagrams153
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Black Body Radiation and Earth’s Temperature169
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Magnetism and Types of Magnets28
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Magnetic Fields30
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Electromagnetism, The Right Hand Grip Rule and Solenoids40
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The Motor Effect55
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Fleming's Left Hand Rule41
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Electric Motors and Loudspeakers25
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Induced Potential, The Generator Effect and Microphones52
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Transformers and their Equations137
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Our Solar System and Orbital Motion184
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The Life Cycle of Stars100
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Red Shift and The Big Bang81
