P4 Electricity

Question 2

What is the size of an electric current

Answer 2

The rate flow of charge

Question 3

What does a cell do

Answer 3

Provides a ‘push’ for electrons in a circuit

Question 4

What does a voltmeter do

Answer 4

Measures the potential difference (voltage)

Question 5

What does an ammeter do

Answer 5

Measures current

Question 6

What does a lamp do

Answer 6

Emits light when current passes through it

Question 7

What is an LDR

Answer 7

Light dependent resistor

Question 8

What does a fuse do

Answer 8

Melts and breaks the circuit if the current is too high

Question 9

What does a resistor do

Answer 9

Limits the current in a circuit

Question 10

What does an LED do (Light Emitting Diode)

Answer 10

Emits light when current passes through it

Question 11

What does a switch do

Answer 11

Enables the current in a circuit to be switched on/off

Question 12

What is a thermistor

Answer 12

Temperature dependent resistor

Question 13

What does a variable resistor do

Answer 13

Allows current in to be varied

Question 14

How is charge carried around the circuit

Answer 14

It is transported by millions of electrons. The electrons transfer energy from the power source to the components in the circuit.

Question 15

What is resistance

Answer 15

A measure of how much a material tries to stop electricity passing through it

Question 16

What happens in metals when there is high resistance

Answer 16

More collisions occur and electrical energy is wasted as light and heat. The current decreases and the metal gets hotter

Question 17

Relation between resistance and current

Answer 17

The larger the resistance, the smaller the current

Question 18

How is resistance affected in a series circuit

Answer 18

When two or more resistors are connected in series, the combined resistance is higher than the individual resistors as there is only one path for the current to travel.

Question 19

Component characteristics practical step 1

Answer 19

Collect all the equipment cell, variable resistor, wires, ammeter, voltmeter, switch, resistor, filament lamp, diode

Question 20

Component characteristics practical step 2

Answer 20

Set up the circuit

Question 21

Component characteristics practical step 3

Answer 21

Enter the component to be tested into the circuit.

Question 22

Component characteristics practical step 4

Answer 22

Set the variable resistor to maximum and turn on the switch.

Question 23

Component characteristics practical step 5

Answer 23

Record the current on the ammeter and the voltage on the voltmeter.

Question 24

Component characteristics practical step 6

Answer 24

Move the slider on the variable resistor to four more positions and repeat step 5

Question 25

Component characteristics practical step 7

Answer 25

Repeat the experiment with other components

Question 26

Current-potential difference graph

Answer 26

Line curves away from the y-axis. So the current is not directly proportional to the potential difference. This filament lamp is a non-ohmic conductor.

Question 27

Current-potential difference graph diode

Answer 27

The line curves towards the y-axis. So the current is not directly proportional to the potential difference. The resistance changes as the current changes. A diode is a non ohmic conductor.

Question 28

Rule of current in a series circuit

Answer 28

In a series circuit, the same current passes through each component

Question 29

Rule of potential difference in a series circuit

Answer 29

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

Question 30

What happens if you add more resistors in a series circuit

Answer 30

It increases the total resistance because the current through the resistors is reduced and the total potential difference across them is unchanged.

Question 31

Rule of current in parallel circuits

Answer 31

The total current through the whole circuit is the sum of the currents through the separate branches.

Question 32

Rule of potential difference in a parallel circuit

Answer 32

The potential difference across each component is the same

Question 33

Rules of resistors in parallel circuits

Answer 33

The total resistance of two (or more) components in parallel is less than the resistance of the resistor with the least resistance.

Question 34

What happens if you add more resistors to a parallel cirucit

Answer 34

The total resistance is decreased