[P2] Electricity

What is the circuit symbol for a bulb?

Circle with a cross

What is the circuit symbol for a cell?

Two lines, one shorter than the other

What is the circuit symbol for a battery?

Two lines, one shorter than the other, repeated at least twice

What is the circuit symbol for an ammeter?

Circle with an A

What is the circuit symbol for a voltmeter?

Circle with a V

What is the circuit symbol for a switch?

A break in the wire line

What is the circuit symbol for a fuse?

Rectangle with a line through

What is the circuit symbol for a diode?

Circle with an arrow and line inside

What is the circuit symbol for a LED?

Circle with an arrow and line inside and two arrows pointing out

What is the circuit symbol for a resistor?

Rectangle

What is the circuit symbol for a variable resistor?

Rectangle with an arrow through

What is the circuit symbol for a thermistor?

Rectangle with a bent line through

What is the circuit symbol for an LDR?

Rectangle with a circle around and two arrows pointing in

What is the function of an electrical cell?

Provides energy to the electrons, or provides potential difference

What is the function of a battery?

Provides energy to the electrons, or provides potential difference

What is the function of a fuse?

Breaks and stops the circuit if the current is too high

What is the function of a switch?

Breaks or completes the circuit

What charge do electrons have?

Negative

What equation links current, charge flow & time?

charge flow = current × time

What is the unit for charge flow?

Coulombs, or C

What is the unit for current?

Amps, or A

What is the unit for time?

Seconds, or s

What happens to current flow if the resistance increases?

Decreases

What equation links current, resistance & potential difference?

potential difference = current × resistance

What is the unit for potential difference?

Volts, or V

What is the unit for resistance?

Ohms, or Ω

What is the function of an ammeter?

Measures the current in a circuit

What is the function of a voltmeter?

Measures the potential difference through a component

Where should an ammeter be placed in a circuit?

In series with the components

Where should a voltmeter be placed in a circuit?

On a parallel bridge around the component of interest

What is the function of a resistor?

Increases the resistance of a circuit

What is the function of a variable resistor?

Increases the resistance of a circuit, and can be changed

What is an ohmic conductor? (2)

The current through an ohmic conductor (at a constant temperature) is directly proportional to the potential difference across it

This means that the resistance remains constant as the current changes

What does the current-potential difference graph for an ohmic conductor (like a resistor) look like?

A straight line through 0,0

What does the current-potential difference graph for a filament bulb look like?

A curved line through 0,0

What is the function of a bulb?

Produces light radiation

What does the current-potential difference graph for a diode look like?

A curved line that increases significantly after a certain potential difference

What is the function of a diode?

Allows current to only flow in one direction

What is the function of an LED?

Allows current to only flow in one direction, and produces light radiation

What happens to the resistance of a thermistor when the temperature changes?

The resistance of a thermistor decreases as the temperature increases.

What is the function of a thermistor?

Increases the resistance of a circuit depending on the temperature of the surroundings

What happens to the resistance of an LDR when the light intensity changes?

The resistance of an LDR decreases as light intensity increases.

What is the function of an LDR?

Increases the resistance of a circuit depending on the brightness of the surroundings

How are thermistors used?

in circuits as thermostats

How are LDRs used?

in circuits to switch on lights on when it gets dark

Give four examples of non-ohmic conductors

Diodes, filament bulbs, LDRs, thermistors

What does 'components in series' mean?

The same electrons flow through each component

What does 'components in parallel' mean?

The same electrons doesn’t flow through the components because they are on different branches of a circuit

What happens to current through components connected in series?

there is the same current through each component

What happens to the total resistance of components connected in series? (2)

the total resistance of the components is the sum of the resistance of each component

adding more components increases the resistance

What happens to the potential difference across components connected in series?

the total potential difference of the power supply is shared between the components

What happens to current through components connected in parallel? (2)

the current splits across the components

the total current through the whole circuit is the sum of the currents through the separate components

What happens to the total resistance of components connected in parallel? (3)

the total resistance is less than the resistance of the smallest individual resistor

the total resistance decreases as more components are added

this is because each new branch provides an additional path for charge to flow

What happens to the potential difference across components connected in parallel?

the potential difference across each component is the same

What is the unit for power?

Watts, or W

What equation links current, resistance & power?

power = current² × resistance

What equation links potential difference, current & power?

power = potential difference × current

What does the amount of energy an appliance transfers depend on?

how long the appliance is switched on for and the power of the appliance

What equation links power, energy transferred, and time?

energy transferred = power × time

What equation links power, charge flow, and potential difference?

energy transferred = charge flow × potential difference

What is the unit for energy transferred?

Joules, or J

What is the unit for work done?

Joules, or J

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] How is the equation 𝙥𝙤𝙩𝙚𝙣𝙩𝙞𝙖𝙡 𝙙𝙞𝙛𝙛𝙚𝙧𝙚𝙣𝙘𝙚 𝙖𝙘𝙧𝙤𝙨𝙨 𝙥𝙧𝙞𝙢𝙖𝙧𝙮 𝙘𝙤𝙞𝙡 𝙭 𝙘𝙪𝙧𝙧𝙚𝙣𝙩 𝙞𝙣 𝙥𝙧𝙞𝙢𝙖𝙧𝙮 𝙘𝙤𝙞𝙡 = 𝙥𝙤𝙩𝙚𝙣𝙩𝙞𝙖𝙡 𝙙𝙞𝙛𝙛𝙚𝙧𝙚𝙣𝙘𝙚 𝙖𝙘𝙧𝙤𝙨𝙨 𝙨𝙚𝙘𝙤𝙣𝙙𝙖𝙧𝙮 𝙘𝙤𝙞𝙡 𝙭 𝙘𝙪𝙧𝙧𝙚𝙣𝙩 𝙞𝙣 𝙨𝙚𝙘𝙤𝙣𝙙𝙖𝙧𝙮 𝙘𝙤𝙞𝙡 used?

To relate the input and output quantities for a transformer

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] In a transformer, which coil is the primary coil?

The coil with an alternating power supply connected to it

[𝗛𝗶𝗴𝗵𝗲𝗿 𝗧𝗶𝗲𝗿] In a transformer, which coil is the secondary coil?

The coil without an alternating power supply connected to it

What colour is the neutral wire?

Blue

What is name of the blue wire in a plug?

Neutral

What colour is the earth wire?

Green and yellow stripes

What is name of the green and yellow striped wire in a plug?

Earth

What colour is the live wire?

Brown

What is name of the brown wire in a plug?

Live

What is the purpose of the neutral wire?

Completes the circuit

What is the purpose of the live wire?

Provides the alternating potential difference

What is the purpose of the earth wire? (2)

Protects the circuit and stops the appliance casing from becoming live

It only carries current if there is a fault

What is the pd of the neutral wire?

0 V

What is the pd of the live wire?

230 V

What is the pd of the earth wire?

0 V (unless there is a fault)

What is the national grid?

a system of cables and transformers linking power stations to consumers

What is the potential difference of mains electricity?

230 V

What is the frequency of mains electricity?

50 Hz

What type of current is mains electricity?

Alternating current (caused by an alternating potential difference)

What is direct current (d.c.)? (2)

Current flows in one direction around the circuit, due to a direct potential difference

It is supplied by cells and batteries

What is alternating current (a.c.)? (2)

Current changes (alternates) direction, due to a potential difference where the positive and negative ends alternate

It is supplied by mains electricity

Why does the national grid transmit electricity at very high potential differences?

Less energy is lost, which makes it more efficient

What happens at step-up transformers?

potential difference increased (current lowered)

What happens at step-down transformers?

potential difference lowered (current increased)

Why do we need step-down transformers?

Electricity has to be reduced to mains potential difference (230V) to be safe for use in homes

How do like charges react to one another?

They repel

How do opposite charges react to one another?

They attract

What contact force is able to move electrons from the surface of one material to another?

Friction

Why is charge able to build up on insulating materials?

They do not conduct charge well

What happens to the charge of a material that loses electrons?

It becomes positively charged

What happens to the charge of a material that gains electrons?

It becomes negatively charged

In what direction do field lines point around a negative charge?

They point towards the source

In what direction do field lines point around a positive charge?

They point away from the source