Topic 4 - Electricity and Static Electricity (GCSE Edexcel Combined Physics Retrieval Questions)

What is the relative charge of an electron?

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What is the overall charge of atoms and why?

Neutral because there are the same amount of electrons and protons.

How do like charges interact?

They repel.

How do opposite charges interact?

The attract.

What does earthing do?

Removes excess charge by movement of electrons

What is the difference between and cell and battery?

A battery is two or more cells

What is does a resistor do?

A resistor limits the flow of current.

What is a thermistor?

The resistance of a thermistor depends on its temperature. As its temperature increases, its resistance decreases and vice versa

What is a light-dependent resistor (LDR)?

The resistance of an LDR depends on the light intensity. As the light intensity increases, its resistance decreases and vice versa

What is a diode?

A diode allows current to flow in one direction only.

What is an ammeter and where is it connected in a circuit?

Used to measure the current in a circuit. Connected in series with other components

What is a voltmeter and where is it connected in a circuit?

Use to measure the potential difference of an electrical component. Connected in parallel with the relevant component

Which components have negligible resistance?

Ammeters and Voltmeters

What is a complete circuit?

A circuit in a complete loop so electrons can flow.

What is the definition of current?

The rate of flow charge

Give the equation linking current, time and charge.

Charge = Current x Time

What is the unit for current?

Amps (A)

What is the unit of charge?

Coulombs (C)

Which direction do electrons flow?

Negative to Positive

What direction is convential current?

Positive to Negative

What is the definition of potential difference?

The amount of energy transferred per unit of charge passing through the terminals

What is the unit of potential difference?

Volts (V)

Give the equation linking potential difference, charge and energy.

Potential Difference = Energy/Charge

When does a current flow?

When the circuit is closed and there is a source of potential difference.

How does resistance change with length of wire?

A longer length of wire has more resistance than a shorter length of wire.

Give the equation linking potential difference, current and resistance.

Voltage = Current x Resistance

What is the unit of resistance?

Ohms (Ω)

In series circuits, how does current behave through components?

The current remains the same through all components.

In parallel circuits, how does current behave at junctions?

Current is shared between junctions.

In series circuits, how is total resistance calculated?

The sum of resistance of all the components.

In series circuits, how is total voltage calculated?

The sum of the voltage across all the components.

In parallel circuits, how does the total resistance change when a resistor is added?

It always decreases

What is the effect of connecting two identical resistors in parallel?

Resistance is halved

What can we say about the potential difference across parallel branches in a circuit?

It is the same for each branch

Describe or draw an I-V graph look like for a fixed resistor.

Directly proportional graph

Describe or draw an I-V graph look like for a filament lamp.

S-Curve

Describe or draw an I-V graph look like for a diode.

y=0 graph until current is allowed through and then a curved positive line

What is an ohmic conductor?

Where current and voltage are directly proportional?

How does an LDR's resistance change with light intensity?

As the light intensity increases the resistance of an LDR decreases and vice versa.

How does a thermistor's resistor change with temperature?

As the temperature increases the resistance of a thermistor decreases and vice versa.

How can you vary current in a circuit?

Using a variable resistor.

When electrical current does work against electrical resistance, what happens to this energy?

Electrical energy is dissipated as thermal energy in the surroundings.

How is the amount of heat energy produced related to current?

The greater the current, the more heat that is produced.

Why does a wire heat up and cause a higher resistance?

As the electrons pass through the metal lattice they collide with ions which vibrate more more.

How can you reduce heating in wires?

Reduce current and use wires with a lower resistance.

What is a danger of heating in wires?

Fire hazard and sparks.

Give the equation linking power, current and voltage.

Power = Current x Potential Difference

Give the equation linking energy, current, potential difference and time.

Energy = Current x Potential Difference x Time