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Physics > Circuit, Potential difference, and Resistance > Flashcards

Circuit, Potential difference, and Resistance Flashcards

1
Q

What is the function of a cell/battery?

A

.Provides the circuit with a source of potential difference.

.A battery is two or more cells.

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2
Q

What is the function of a switch?

A

.It turns the circuit on (closed), or off (open)

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3
Q

What is the function of a fixed resistor?

A

.It limits the flow of current.

.And it has a fixed resistance that cannot be changed.

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4
Q

What is the function of a variable resistor ?

A

.It is a resistor with a slider that is used to change the resistance.

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5
Q

What is the function of a thermistor?

A

.The resistance of the thermistor depends on the temperature.

.So if the temperature increases, the resistance decreases.

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6
Q

What is the function of a light-dependent resistor (LDR)?

A

.The resistance of an LDR depends on the light intensity.

.So as the light intensity increases, the resistance decreases.

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7
Q

What is the function of a diode?

A

.A diode allows the current to flow in one direction only.

.They are also used to convert AC to DC current.

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8
Q

What is the function of a Light-emitting diode (LED)?

A

.It emits light when a current passes through it.

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9
Q

What is the function of a ammeter?

A

.It used to measure the current.

.It is also in a series circuit with other components.

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10
Q

What is the function of a voltmeter?

A

.It is used to measure the potential difference.

.It is connected in a parallel circuit with relative components.

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11
Q

What do electric circuit diagrams require to work effectively?

A

.An energy source: For the current to flow.

.A closed path or a complete circuit: Electrons need to flow in a complete loop for the current to flow.A circuit can be closed and open using a switch.

.Electrical components: These could act as sensors that respond to the environment (LDR, Thermistor) etc.

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12
Q

What is the direction of current flow?

A

.From positive to negative terminal.

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13
Q

What is electric current?

A

.It is the flow of electrical charge.

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14
Q

State the equation linking charge, current, and time.Give the units for the quantities involved.

A

.Charge = current x time

.Q=I x t

.Charge (coulombs), Current (Amperes), Time (seconds).

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15
Q

What can be said about the value of current at any point in a single loop?

A

.Current is the same at all points in a closed loop.

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16
Q

What two factors the current in a circuit depend on ?

A

.Potential Different (V)
.Resistance (R)

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17
Q

What equation should be used to calculate potential difference if current and resistance are known? State the units for all 3 quantities .

A

.Potential difference = current x resistance

.V= I x R

.Potential difference (V), Current (A), Resistance (ohms)

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18
Q

Define conventional current.

A

.The flow of positive charge from the positive terminal of a cell to the negative terminal.

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19
Q

Define potential difference.

A

.The amount of energy transferred by each coulomb of charge as it passes through a component.

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20
Q

Define current.

A

.Flow of charge around a circuit.

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21
Q

Define resistance

A

.It’s the restriction of the flow of current.

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22
Q

Do insulators have high or low resistance?

A

. They have a high resistance as there is lower current.

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23
Q

Do conductors have high or low resistance?

A

.They have a low resistance as they are good conductors of heat and electricity.

.Which means there is higher current.

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24
Q

How can you increase the resistance of a circuit?

A

.By adding fixed or variable resistors to it.

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25
Q

What is a charge?

A

Charge is a property carried by charged particles.

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26
Q

How to calculate resistance.

A

Resistance = Potential difference divided by current.

R = V/I

Resistance (ohms), Potential difference (V), Current (A)

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27
Q

What do we need to investigate how the length of a wire at a constant temperature affects the resistance of electrical circuits?

A

Power supply
Wires
Crocodile Clips
Ammeter
Voltmeter
Resistors
Thin resistance wire
Metre ruler.

28
Q

What is the purpose of using a power supply/cell/battery in the experiment?

A

.To provide a source of potential difference to the circuit

29
Q

What is the purpose of using wires in the experiment?

A

.To connect all the components in the circuit.

30
Q

What is the purpose of using crocodile clips in the experiment?

A

.To connect different lengths of the resistance wire.

31
Q

What is the purpose of using an ammeter in the experiment?

A

.To measure the current through the circuit.

32
Q

What is the purpose of using a voltmeter in the experiment?

A

.To measure the potential difference.

33
Q

What is the purpose of using resistors and a thin resistance wire in the experiment?

A

.To measure the resistance of.

34
Q

What is the purpose of using a metre ruler in the experiment?

A

To measure the length of resistance wire.

35
Q

Investigate the length of a resistance wire at a constant temperature.

A

Step 1:
Set up the equipment by connecting two crocodile clips to the thin resistance wire a distance of 10 apart and setting the power supply to 1.5V

Step 2:
Connect the wire, using the clips, to the rest of the circuit.

Step 3:
Record the potential difference from the voltmeter and current from the ammeter.

Step 4:
Move the clips in 10cm intervals further apart.

Step 5: Take new measurements from the voltmeter and ammeter for each reading.

Step 6:
Continue until the crocodile clips are length of 1m apart.

36
Q

What is the independent, dependent, and control variables of this experiment?

A

Independent variable: Length of resistance wire

Dependent variable: Resistance

Control variables: Potential difference of the power supply and temperature of the wire.

37
Q

What is a zero error?

A

.It is a reading on a measuring equipment like an ammeter when the value should be zero

38
Q

What is a systematic error?

A

.It’s when there are faults in the methods which affects every measurement.

For example, a zero error. This affects accuracy.

39
Q

What is a random error?

A

.It’s the unpredictable changes in an experiment which affects precision.

40
Q

What are some systematic errors in this experiment?

A

.The first crocodile (which is connected to the circuit not the wire) must start at zero on the ruler.

.Otherwise, this could cause a zero error in the measurements of the length.

.Both the ammeter and voltmeter should be checked to start from zero.

41
Q

What are some random errors in this experiment?

A

.The current should be switched off between readings so it’s temperature doesn’t affect it’s resistance.

.Repeat the experiment by reducing the length of the wire 10cm each time down to a length of 10cm

.Add more resistors in series and parallel to calculate the effect on the combined resistance.

42
Q

What are some safety considerations of this experiment?

A

.Make sure there are no liquids close to the equipment as this could damage electrical equipment if spilled.

43
Q

What is the Ohm’s law?

A

.The Ohm’s law states that:

.The current is directly proportional to the potential difference.

44
Q

What are ohmic conductors?

A

.They are electrical conductors that obey the Ohm’s law.

45
Q

What are some examples of ohmic conductors?

A

.Fixed resistors
.Wires
.Heating elements

46
Q

What is the ohms law equation?

A

V= I x R

47
Q

What is the relationship between the current through an ohmic conductor and the potential difference across the resistor? Does the resistance of the conductor change as the current varies? Please explain your answer.

A

The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across the resistor. This means that the resistance remains constant as the current changes.

48
Q

What happens to the resistance of filament lamp as the temperature increases?Why?

A

.The resistance increases.

.Ions in the metal have more energy, which makes them vibrate more, causing collisions between electrons as they flow through the metal.

49
Q

What is different about current flow through a diode?

A

.The current only flows in one direction.

.The resistance is very high in the other direction, preventing current flow.

50
Q

State what happens to the resistance of a thermistor as temperature increases.

A

.The thermistor’s resistance decreases.

51
Q

Give two examples of when a thermistor may be used.

A

.In a thermostat to turn a heater on below a certain temperature

.In a freezer to turn on a cooler when the temperature becomes too high.

52
Q

State what happens to the resistance of a LDR as light intensity decreases.

A

.The LDR’s resistance increases.

53
Q

Give an application for a LDR.

A

.Street lights often use LDRs

.When light levels become too low, the light gains sufficient energy to turn on

54
Q

What are example of non-ohmic conductors.

A

.Filament lamps
.Diodes and LEDs
.LDRs
.Thermistors.

55
Q

Investigate how combinations of resistors in series and parallel affect the total resistance in electrical circuits.

A

.Step 1:
Connect the series circuit with a battery of 4V, first with one resistor (R1) with the a voltmeter connected in parallel and ammeter in series.

Step 2:
Close the switch and record the reading on the voltmeter and ammeter.

Step 3:
Repeat the steps 1 and 2 for the second resistor (R2)

Step 4:
Open the switch and add connect both R1 and R2 in series, connecting the voltmeter in parallel to both resistors

Step 5:
Close the switch and record the new readings on the voltmeter and ammeter.

Step 6:
Open the switch and arrange R1 and R2 now in parallel

Step 7:
Close the switch and record the readings on the voltmeter and ammeter.

56
Q

What does this experiment tells us about the resistance of a series circuit?

A

.The resistance of the combined resistors is equal to the sum of the two individual resistances.

.This is because the electrons flow through just one path through both resistors, so the current does too.

57
Q

What does this experiment tells us about the resistance of a parallel circuit?

A

.The resistance of the combined resistors is less than the sum of the two individual resistances

.This is because the electrons are split between the different paths (or ‘loops’) but the resistors still have the same potential difference across them

58
Q

What are some random errors in this experiment?

A

.Add more resistors in series and parallel to calculate the effect on the combined resistance.

59
Q

What are some safety considerations in this experiment?

A

.Switch off the power supply right away if burning is smelled.

60
Q

Investigate the resistance in thermistors.

A

For the thermistor circuit:
Begin with the heater turned off
Record the reading on the voltmeter and ammeter
Slowly increase the heat of the heater using the dimmer switch
Record the reading on the voltmeter and ammeter for each increase in temperature of the heater

61
Q

Investigate the resistance in LDRs

A

For the LDR circuit:
Begin with the lamp turned off in a dark room
Record the reading on the voltmeter and ammeter
Slowly increase the light intensity of the lamp using the dimmer switch
Record the reading on the voltmeter and ammeter for each increase in light intensity

62
Q

In an electronics experiment, a lamp and a heater are placed close to an LDR and a thermistor, respectively. What should the experimenter do before taking readings with the voltmeter and ammeter, and what should they do to calculate the resistance of the LDR and thermistor for each change in light intensity or temperature?

A

Wait a few seconds before taking the voltmeter and ammeter readings to allow the LDR and thermistor to react to the change in the environment

Calculate the resistance of the LDR or thermistor for each change in light intensity or temperature using the equation: R= V/I

63
Q

What equipments should you need to investigate I-V characteristics of many circuit elements?

A

.Ammeter
.Voltmeter
.Variable resistor
.Fixed resistor ( between 100 Ω and 500 Ω))
.Filament lamp
.Diode
.Voltage supply
.Wires.

64
Q

investigate the I–V characteristics of a variety of circuit elements

A

Step 1:
Set up the circuit as shown with the fixed resistor

Step 2:
Vary the voltage across the component by changing the resistance of the variable resistor, using a wide range of voltages (between 8-10 readings). Check the appropriate voltage reading on the voltmeter

Step 3:
For each voltage, record the value of the current from the ammeter 3 times and calculate the average current

Step 4:
Increase the voltage further in steps of 0.5 V and repeat steps 2 and 3

Step 5:
Make sure to switch off the circuit in between readings to prevent heating of the component and wires

Step 6:
Reverse the terminals of the power supply and take readings for the negative voltage (and therefore negative current)

Step 7:
Replace the fixed resistor with the filament lamp, then the diode, repeating the experiment for each

65
Q

What are some systematic errors in the experiment?

A

.The voltmeter and ammeters should start from zero, to avoid zero error in the readings

66
Q

What are some random errors in this experiment?

A

In practice, the voltmeter and ammeter will still have some resistance, therefore the voltages and currents displayed may be slightly inaccurate

. The temperature of the equipment could affect its resistance. This must be controlled carefully

. Taking multiple readings of the current for each component will provide a more accurate result and reduce uncertainties

67
Q

What are some safety considerations in this experiment?

A

. Switch off the power supply right away if burning is smelled

. Make sure there are no liquids close to the equipment, as this could damage the electrical equipment

. The components will get hot especially at higher voltages
Be careful when handling them - especially the filament lamp

. Disconnect the power supply in between readings to avoid the components heating up too much

Physics (6 decks)

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