P2 Revision

Question 1

What are components

Answer 1

A device in an electric circuit, such as a battery, switch or lamp

Question 2

What is a fixed resistor

Answer 2

restricts or limits the flow of electrical current, the resistance does not change

Question 3

Variable resistor

Answer 3

A resistor where the value of the resistance can be changed

Question 4

Thermistor

Answer 4

An electrical device whose resistance decreases as its temperature increases- can be used in thermostats

Question 5

Light dependent resistor (LDR)

Answer 5

A type of resistor which is affected by changes in light levels. Low light levels = high resistance, higher light intensity = resistance decreases

Question 6

Name 2 types of current

Answer 6

• direct
• alternating

Question 7

What happens in a direct current

Answer 7

The flow of electrons is in one direction only

Question 8

What happens in alternating current

Answer 8

The direction of electron flow continually reverses

Question 9

What is charge

Answer 9

A property of a body which experiences a force in an electric field (measured in coulombs)

Question 10

What is the equation for charge

Answer 10

Charge = current x time
Q = I x t
Charge = coulombs
Current = amps
Time = seconds

Question 11

What is current measured by

Answer 11

An ammeter

Question 12

What does the current depend on

Answer 12

• the resistance of the component
• potential difference across the component

Question 13

How do you measure potential difference across a component

Answer 13

A voltmeter must be placed in parallel with that component
- potential difference is known as voltage

Question 14

What is the equation for potential difference

Answer 14

Potential difference = energy/charge
V = E/Q

Question 15

What is the resistance over a longer piece of wire compared to a shorter piece of wire

Answer 15

The resistance is higher over a longer piece of wire. Resistance is directly proportional to length of wire

Question 16

What is a diode

Answer 16

An electrical device that allows current to flow in one direction only

Question 17

What is Ohm’s law

Answer 17

The rule that states that the current is directly proportional to the voltage across the resistor - provided that temperature remains constant

Question 18

What is the series circuit?

Answer 18

A circuit, where one component follows directly from another.

Question 19

Important key facts for series circuits

Answer 19

Current is the same through each component
The total potential difference of the power supply is shared between the components
The total resistance of the circuit is the sum of individual resistors

Question 20

What does current do in a parallel circuit

Answer 20

The current will split
An ammeter can show/measure how the current splits

Question 21

What happens to potential difference (voltage) in a parallel circuit

Answer 21

The potential differences is supplied equal across each of the parallel components

Question 22

What happens when resistors are added to a parallel circuit?

Answer 22

The overall resistance is reduced as the current (electrons) may follow multiple paths

Question 23

Why do wires heat up

Answer 23

Electrons flowing through wires, collide with ions Which causes the ions to vibrate more. increasing temperature.

Question 24

Power and measurements

Answer 24

Power (watts) = current (amps) x potential difference (volts)

Power(watts) = current^2(amps)
x resistance (ohms)

Question 25

What colour are the earth, neutral and live wire

Answer 25

Earth = green and yellow
Neutral = blue
Live = brown

Question 26

What is the national grid

Answer 26

The network that connects all the power stations in the country to make sure that everywhere has access to electricity

Question 27

What are transformers?

Answer 27

An electrical device that increases or decreases the potential difference (voltage) of an alternating current

Question 28

Why do objects sometimes become electrically charged when rubbed against each other

Answer 28

Electrons which are negatively charge may be ‘rubbed off’ one material and onto the other. Leaves a positive and negative charge on the objects

Charges may attract or repel

Question 29

How to draw an electric field

Answer 29

Arrow drawn from positive to negative charge
Closer together arrows are, stronger the force