electricity

Question 1

What 2 things are needed for a charge to flow?

Answer 1

~The circuit must be closed (no open switches)
~Must have a source of potential difference

Question 2

What is current?

Answer 2

The flow of electrical charge.

Question 3

What does Q = It stand for?

Answer 3

Charge (in coulombs) = current (in amps) x time (in seconds).

Question 4

Current through a component depends on…

Answer 4

~The resistance of the component
~The potential difference across the component

Question 5

What does V = IR stand for?

Answer 5

Potential difference (in volts) = current (in amps) x resistance (in ohms).

Question 6

What is the gradients for a resistor, filament lamp or diode graph?

Answer 6

1 / resistance.

Question 7

How does resistance change with current?

Answer 7

~When current is increased electrons have more energy
~They collide with atoms in the resistor when they flow through it
~This transfers energy to the atoms causing them to vibrate more
~Making it more difficult for electrons to flow through the resistor

Question 8

As resistance increases…

Answer 8

Current decreases.

Question 9

How does resistance change with temperature in normal wires?

Answer 9

Same as with current as the atoms vibrate when hot.

Question 10

How does resistance change with temperature in a thermistor?

Answer 10

Hotter temperatures mean the resistance is lower.

Question 11

How does resistance change with length?

Answer 11

The greater the length the more resistance and the lower the current (electrons have to go through more resistor atoms).

Question 12

How does resistance change with light in an LDR?

Answer 12

The greater the light intensity, the lower the resistance.

Question 13

How does resistance change with voltage in diodes?

Answer 13

Diodes allow current to flow freely in one direction but in the opposite direction, it has a very high resistance so no current can flow.

Question 14

In series circuits, current only flows…

Answer 14

In a single path.

Question 15

In series circuits, current is the same…

Answer 15

Everywhere.

Question 16

In a series circuit, potential difference…

Answer 16

Is shared across the whole circuit.

Question 17

In a series circuit, the potential difference of the power supply =

Answer 17

The sum of the potential difference across each component.

Question 18

In parallel circuits, current…

Answer 18

Splits into multiple paths.

Question 19

In a parallel circuit, potential difference is the same…

Answer 19

Across each branch.

Question 20

In a parallel circuit, the potential difference of the power supply =

Answer 20

The potential difference of each branch.

Question 21

Why does the potential difference of the power supply = the potential difference of each branch in a parallel circuit?

Answer 21

Because the charge can only pass through any one branch.

Question 22

In a parallel circuit, current is shared…

Answer 22

Between each branch.

Question 23

In a parallel circuit, current through source =

Answer 23

Sum of current through each branch.

Question 24

In a parallel circuit, total resistance is less than…

Answer 24

The branch with the smallest resistance.

Question 25

What colour is the live wire?

Answer 25

Brown

Question 26

What is the potential difference of the live wire?

Answer 26

230V.

Question 27

What does the live wire carry?

Answer 27

Alternating potential difference from the supply.

Question 28

What colour is the neutral wire?

Answer 28

Blue.

Question 29

What is the potential difference of the neutral wire?

Answer 29

0V.

Question 30

What does the neutral wire do?

Answer 30

Completes the circuit.

Question 31

What colour is the earth/safety wire?

Answer 31

Green and yellow striped.

Question 32

What is the potential difference of the earth/safety wire?

Answer 32

0V.

Question 33

What is the function of the earth/safety wire?

Answer 33

To carry current, only if there is a fault.

Question 34

What is the earth/safety wire connected to?

Answer 34

The earth and the casing.

Question 35

What is power?

Answer 35

Energy transferred per second.

Question 36

What 2 things is power directly proportional to?

Answer 36

Current and voltage.

Question 37

What is the equation for energy transferred?

Answer 37

Energy transferred= power x time or energy transferred = charge x potential difference.

Question 38

What energy is transferred in a motor?

Answer 38

Kinetic energy.

Question 39

What energy is transferred in a kettle?

Answer 39

Thermal energy.

Question 40

What is work done in appliances?

Answer 40

When charge flows through a circuit (and is equal to energy transferred) and all energy is transferred to the appliance.

Question 41

What is the power rating of an appliance?

Answer 41

The power the appliance uses in watts.

Question 42

The higher the power rating…

Answer 42

The more energy the appliance uses.

Question 43

What is the national grid?

Answer 43

A system of cables and transformers linking power stations to consumers across the UK.

Question 44

What do step-up transformers do?

Answer 44

Increase the potential difference from the power station to the national grid.

Question 45

In step-up transformers, as power is constant…

Answer 45

Current decreases so less energy is lost.

Question 46

What do step-down transformers do?

Answer 46

Decrease the potential difference from the national grid to consumers for their safety.

Question 47

When 2 insulators are rubbed together…

Answer 47

~Electrons are transferred from one object to another ~This forms a positive charge on one object and a negative charge on the other

Question 48

Why do sparks occur?

Answer 48

When a charge jumped through the air from a highly negative object to a highly positive object to try balance the charges.