Physics - Electricity

What is electric current?

The flow of elctrical charge.

The greater the rate of flow, the higher the current.

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What is current measured in?

Amperes (A) using an Ammeter.

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What is charge measured in?

Coulombs (C)

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What is Potential Difference?

tells us the electrical potential from one point in a circiut to another.

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What is Charge?

Amount of electricity travelling in a curcuit.

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What is Potential Difference measured in?

Volts (V) using a voltmeter.

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What does Q, I, t, R, V, P stand for?

Q- Charge

I- Current

t- time

R- Resistance

V- Potential Difference

P- Power

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What is the difference between an ammeter and a vo

A- Set up in series with components

V- Set up parallel to components

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What is resistance and what is it measured in?

It is a measurement of how much current flow is reduced.


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How do you work out Charge?

Charge = Current x time

Q = I x t

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How do you work out Resistance?

Resistance = Potential Difference      /          R = V

                              Current                                    I

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What happens if the resistance is higher?

Reduces current.

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What does increasing voltage do?

Increases current.

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Describe an ohmnic conductor-potential difference

At a constant temperature, current is directly proportional to the potential difference across the resistor.

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Describe a filament lamp-potential difference grap

As current increases, the resistance increases. The temperature increases as current flows.

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Describe a Diode-Potential Difference graph.

Current flows when potential difference flows forward. Very high resistance in reverse.

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What does the National Grid do?

Distributes electricity in power stations around the UK.

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Describe an Alternating Current.

Potential Difference switches direction many times a second, current switches direction (Generator).

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Describe a Direct current.

Potential Difference remains in one direction, current flows the same direction (Cell or Battery).

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What happens with a Thermistor?

Resistance varies with temperature.

Resistance decreases as temperature increases.

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What happens with an LDR?

Resistance varies with light intensity.

Resistance decreases as light increases.

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What is Earthing?

It is a safety device; Earth wire joins the metal case.

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What is Earthing?

It is a safety device; Earth wire joins the metal case.

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Describe the Live wire.


Carries Potential Difference from mains supply.

Potential Difference between live and warth is 230V.

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Describe the Neutral wire.


Completes the circuit.

Potential Difference = OV

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Describe the Earth Wire.

Yellow and Green stripes.

Only carries current if there is a fault.

Potential Difference = 0V

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What is the Frequency of a mains supply?


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Describe a step-up transformer.

Increase Voltage; decrease current.

Increases efficiency, reduces heat loss.

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Describe a step-down transformer.

Decreases voltage, increase current.

Makes safer for houses.

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What is Power meausred in?


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What are the two ways of working out power?

Power = Potential Difference x Current / R = V x I

Power = (current)2 x resistance / P =I2 x R

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How do you work out Energy Transferred?

Energy transferred = Power x time / E = P x t

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Descibe a Series circuit.

A circuit with one loop.

Current is all the same in all components.

Total potential difference is shared between all the components.

Total resistance is less then the resistance value of the smallest individual resistor.

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Descibe a parallel circuit.

A circuit with two or more loops.

Total current is the sum of each component's current.

Potential Difference across all components is the same.

Total resistance is less than the resistance value of the smallest individual resistor.

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Decribe a cell, battery, switch and a bulb.

Cell - Store of chemical energy.

Battery -  Two or more cells in series.

Switch -  Breaks current, turning current off.

Bulb - Lights when current flows.

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Describe an ammeter, voltmeter and diode.

Ammeter - Measures current.

Voltmeter - Measures Potential Difference.

Diode - Current flows one way.

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Describe an LED, LDR, and a fuse.

LED - Emits liught when current flows.

LDR -  Resistance low in bright light.

Fuse - Melts when current is too high.

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Describe a resistor, variable resistor and thermis

Resistor - Affects the size of current flowing.

Variable Resistor - Allows current to be varied.

Thermistor - Resistance low at high temperature.

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