Electricity

Question 1

how are electric circuits shown as diagrams

Answer 1

with circuit symbols and straight lines, components shouldn’t be on corners

Question 2

what is the difference between a battery and a cell

Answer 2

a cell is one and a battery is multiple

Question 3

what determines the size of an electrical current

Answer 3

the voltage of the battery and the resistance of the components

Question 4

what’s the equation including current, charge & time

Answer 4

current = charge / time

Question 5

what is potential difference

Answer 5

a measure of the work done or energy transferred to the lamp by each coulomb of charge that passes through it. The unit of potential difference is the volt (V).

Question 6

what is resistance and what is its unit

Answer 6

a way of saying how difficult it is for electricity to flow through and is measured in ohms Ω

Question 7

what is ohms law

Answer 7

Ohm’s Law is a formula used to calculate the relationship between voltage, current and resistance in an electrical circuit.

Question 8

what happens when you reverse the potential difference across a resistor

Answer 8

it would flow in the opposite direction creating a negative reading

Question 9

what happens to the resistance of a filament lamp as its temperature increases

Answer 9

it increases due to energy being given off through heat

Question 10

how does the current through a diode depends on the potential difference across it

Answer 10

when the potential difference gets low enough all of the reading of current become 0

Question 11

what happens to the resistance of a temperature-dependent resistor as its temperature increases

Answer 11

When temperature increases, the resistance increases

Question 12

what happens to the resistance of a light-dependent resistor as the light level increases

Answer 12

resistance decreases as the light intensity increases

Question 13

Describe the current, potential difference, and resistance for each component in a series circuit

Answer 13

the current is the same at each resistor, the individual potential differences added together, circuit is equal to the sum of individual resistances

Question 14

Describe the potential difference of several cells in series

Answer 14

the total equals the voltage of the power supply

Question 15

how to calculate the total resistance of two resistors in series

Answer 15

Rtotal = R1 + R2 +R3

Question 16

why does adding resistors in series increases the total resistance

Answer 16

increases as more components are added

Question 17

describe the currents and potential differences for components in a parallel circuit

Answer 17

charge divides up into separate branches, circuit is equal to the potential difference of just one of the cells

Question 18

Calculate the current through a resistor in a parallel circuit

Answer 18

I = ΔV / R

Question 19

Explain why the total resistance of two resistors in parallel is less than the resistance of the smaller individual resistor

Answer 19

more current flows from the source than would flow for any of them individually

Question 20

Explain why adding resistors in parallel decreases the total resistance

Answer 20

because there are more paths for the current to pass through

Question 21

which equation includes potential difference, energy transferred & charge

Answer 21

potential difference across a component (V) = energy transferred (E) (joules, J)/ charge (Q) (coulombs, C)

Question 22

which equation includes resistance, potential difference, current

Answer 22

resistance (R) (ohms, Ω) = potential difference (V) (volts, V) / current (I) (coulombs, C)

Question 23

what is direct current and what is alternating current

Answer 23

a direct current is an electric current flowing in one direction only, an alternating current is the flow of electric charge that periodically reverses

Question 24

what is meant by the live wire and the neutral wire of a mains circuit

Answer 24

The wire covered in brown plastic is the live wire. This carries the 230 V alternating potential difference from the power supply. The wire covered in blue plastic is the neutral wire and this completes the circuit from the appliance back to the supply. It is usually at 0 V

Question 25

Describe the National Grid

Answer 25

the network of power stations, powerlines and electricity infrastructure that allows electricity to be generated, transported and used across the country

Question 26

what is the casing of a mains plug or socket made of and explain why

Answer 26

they have plastic casings, or they have been designed so that the live wire cannot touch the casing

Question 27

what is in a mains cable

Answer 27

A plug connects a device to the mains electricity supply

Question 28

what are the colours of the live, neutral, and earth wires

Answer 28

Live Brown
Neutral Blue
Earth Yellow and Green

Question 29

why does a three-pin plug include an earth pin

Answer 29

it provides a path for current to flow from the case of the device to the ground if there is a fault

Question 30

how are power and energy related

Answer 30

Energy is the ability to cause change; power is the rate energy is moved, or used.

Question 31

calculate the energy transferred in a given time

Answer 31

Energy transferred = power x time

Question 32

equation including power, current and potential difference

Answer 32

power supplied (P) (watts, W) = current (I) (amperes, A) x potential difference (V) (volts, V)

Question 33

equation using charge, current and time

Answer 33

Current = charge / time

Question 34

what are the energy transfers when electric charge flows through a resistor

Answer 34

transferred as heat

Question 35

equation including energy transferred, charge and potential difference.

Answer 35

energy transferred = charge x potential difference

Question 36

equation using power, current and potential difference

Answer 36

power supplied (P) (watts, W) = current (I) (amperes, A) x potential difference (V) (volts, V)

Question 37

equation using power, energy transferred and time

Answer 37

Power (P) (watts, W) = energy transferred (E) (joules, J) / time (t) (seconds, s)

Question 38

equation using power, current and resistance

Answer 38

power (P) (watts, W) = current squared (amperes, A) x resistance (R) (ohms, Ώ)

Question 39

equation including charge, current and time

Answer 39

charge flow (Q) (coulombs, C) = current (I) (amperes, A) x time taken (t) (seconds, s)

Question 40

what is a current

Answer 40

stream of charged particles, such as electrons or ions, moving through an electrical conductor or space

Question 41

current equation

Answer 41

current = charge x time

Question 42

how does the resistance of a thermistor change depending on temperate and light intensity?

Answer 42

temperature : decreases as temp increases

light intensity: decreases as light increases

Question 43

how does the resistance of a LDR change depending on temperate and light intensity?

Answer 43

temperature: decreases as temp increases

light intensity: decreases as light increases

Question 44

what are the uses of LDRs and thermistors?

Answer 44

LDRs : detect light levels e.g. automatic security lights

Thermistors: ovens and refrigerators

Question 45

what is the purpose of transformers in the national grid?

Answer 45

lower the voltage and bring it down to a usable level

Question 46

what is the equation involving potential difference and coil?

Answer 46

potential difference across primary coil x current in primary coil = potential difference across secondary coil x current in secondary coil

Question 47

what happens when insulating materials are rubbed against eachother?

Answer 47

they become electrically charged

Question 48

what happens when 2 electrically charged objects are brought close together?

Answer 48

they exert a force on each other. Two charged objects may either pull towards each other (attract) or push each other away (repel).

Question 49

describe an electric field

Answer 49

positive to negative