Electricity and Electromagnetism (F) Flashcards
(24 cards)
Units + symbols for force
F Newton (N)
Units + symbols for magnetic field strength
B tesla (T)
Units + symbols for electric field strength
E volts per meter (V/m)
Units + symbols for distance
d metres (m)
Protons charge is positive….
1.6x10^-19 coulombs (c)
Electrons charge is negative…..
-1.6x10^-19 coulombs (c)
Units + symbols for length
m metre
Units + symbols for electric potential energy
Ep joules (J)
Define current + give symbols and units
Current is the flow of electric charge through a conductor or circuit.
i ampere (A)
Define resistance + give symbols and units
Resistance is a measure of the opposition that a material or component offers to the flow of electric current. It indicates how much a material resists the passage of electric charge through it. The higher the resistance, the more difficult it is for the current to flow through the material.
R ohm (Ω)
Define charge + give symbols and units
Charge is a fundamental property of matter that causes it to experience a force in an electric field. It comes in two different types: positive and negative. Like charges repel and opposite charges attract.
q or Q coulomb (c)
Q= large quantity of charge
q= small quantity of charge
Define voltage + give symbols and units
Voltage (also known as electric field potential difference) is a measure of the energy difference per unit charge between two points in an electric field. It represents the work done to move a unit of positive charge from one point to another in a circuit.
V volt
Explain how magnetic fields are generated
> Moving Charges & Magnetic Fields:
- When electric charges (like electrons) move through a conductor (e.g., a wire), they generate a magnetic field around the wire.
- This is explained by Ampère’s Law: Moving charges produce magnetic fields.
> Permanent Magnets:
- The magnetic field in permanent magnets is caused by the movement of electrons inside the atoms.
- In materials like iron, many of the electrons’ magnetic fields align in the same direction, creating a strong, uniform magnetic field.
> Coil of Wire (Solenoid):
- By coiling a wire and passing an electric current through it, a controllable magnetic field is produced.
- This is an example of an electromagnet—its magnetic field can be:
*Turned on/off by starting or stopping the current.
*Strengthened by increasing the current or adding more coils.
> Core Principle:
Whether it’s a current in a wire, aligned electrons in a magnet, or a current in a coiled wire, moving electric charges are always responsible for generating magnetic fields.
Explain why ammeters have to be in series to the component
> Purpose of an Ammeter:
An ammeter measures the current flowing through a circuit.
> Series Connection:
- To accurately measure current, the ammeter must be in series with the component.
- This ensures that the same current passing through the component also flows through the ammeter.
> Incorrect Placement in Parallel:
- If placed in parallel, the current would bypass the component and flow through the ammeter instead.
- This could result in incorrect measurements or even damage to the ammeter or circuit due to excessive current flow.
> Key Principle:
By being in series, the ammeter allows for the full current through the component to be measured accurately.
Explain why current remains the same across all components in a series, but is shared between the branches in a parallel circuit.
Series Circuit:
In a series circuit, there is only one path for the current to flow through. Because the current has only this single path, it must be the same throughout the circuit. Everyone circuit in the series components has the same current.
Parallel Circuit:
In a parallel circuit, there are multiple paths (branches) for the current to flow through. The total current splits among the different branches. Each branch gets a part of the total current, so the current is shared among the branches.The total current flowing into the parallel circuit is equal to the sum of the currents in each branch.
What happens to the current and voltage in a parallel circuit
> Voltage in Parallel:
- The voltage across each component in a parallel circuit is the same.
This is because all components are connected to the same two points, so they experience the same potential difference.
- Key Point: Voltage is constant across all branches.
> Current in Parallel:
- The total current supplied by the power source is divided among the different branches.
- The current through each branch depends on the resistance of that branch (Ohm’s Law).
- Key Point: The sum of the currents in all branches equals the total current supplied by the source.
> Core Principle:
In parallel circuits, voltage remains constant across components, while current divides based on the resistance of each branch.
What happens to a current and voltage in a series circuit.
Current: The current is the same at every point in a series circuit (constant). This is because there is only one path for the current to flow, so the same amount of charge passes through each component in the circuit.
Voltage: The total voltage across the circuit is the sum of the voltages across each component. This means that if you have multiple components (like resistors) in series, the total voltage supplied by the battery or power source is divided among those components.
How is an electric field formed
An electric field is formed when there is a charged object. When an object has an electric charge (positive or negative), it creates an electric field around it. This is because electric charges exert forces on each other. The electric field can be visualised using field lines. For a positive charge, the lines radiate outward, while for a negative charge, the lines point inward. The direction of the field is the direction a positive test charge would move if placed in the field. The strength of the electric field is stronger closer to the charge and weaker further away. The field lines are denser (closer together) where the field is stronger. In summary, an electric field is created by a charged object and extends through the space around it, with its strength and direction determined by the charge and distance from it.
What is the difference between a parallel and a series circuit
Series Circuit: Components are connected one after the other, so there is only one path for the current to flow. The same current flows through all components in the circuit. The total voltage is divided among the components. If one component fails, the entire circuit is interrupted.
Parallel Circuit: Components are connected across common points, creating multiple paths for the current to flow. The current is divided among the different paths. Each path gets a portion of the total current. All components receive the same voltage. If one component fails, the others continue to operate. In summary, a series circuit has one path for current and divides the voltage, while a parallel circuit has multiple paths for current and the same voltage across all components.
Explain why the voltage is shared across all components in series but remains the same in each parallel branch.
In a series circuit, the voltage is shared across all components because there’s only one path for the current to flow. As the current passes through each component, it loses some energy (voltage) due to resistance. This means that the total voltage provided by the power source is divided among all the components. The sum of the voltages across each component in a series circuit equals the total voltage from the power source. In a parallel circuit, each branch provides a separate path for the current to flow. The voltage across each branch is the same because the ends of each branch are connected to the same two points in the circuit, which are directly connected to the power source. Thus, the potential difference (voltage) across each branch is equal to the total voltage supplied by the power source.
Explain how charged particles (positive and negative) move through an electric field.
Positive Charges: Positive particles (like protons) move away from the positive end of the electric field and towards the negative end. This is because they are repelled by other positive charges and attracted to negative charges.
Negative Charges: Negative particles (like electrons) move towards the positive end of the electric field and away from the negative end. This is because they are attracted to positive charges and repelled by other negative charges. In summary, positive charges move from positive to negative, while negative charges move from negative to positive.
Total resistance in a series circuit
R total = R1 + R2 + R3….
Total resistance in a parallel circuit
1/R total = 1/R1 + 1/R2 + 1/R3….
Total current in any circuit
I total = V supply/R total
