p3

Question 1

what can happen when insulating materials are rubbed together

Answer 1

They become (statically) electrically charged

Question 2

Why can insulators become electrically charged when rubbed together

Answer 2

1. Electrons are rubbed from one material to another
2. The material gaining electrons becomes negatively charged
3. The material losing electrons becomes equally positively charged

Question 3

What is charging

Answer 3

The addition or removal of electons from a material

Question 4

How can charge be detected

Answer 4

Use a gold leaf electroscope; the gold leaf is repelled by positive charge.

Question 5

What happens when two electrically charged objects are bought close together

Answer 5

They exert a force on each other

Question 6

What happens when 2 oppositely charged objects are bought close together

Answer 6

They exert an attractive force on each other and attract

Question 7

What happens when two identically charged objects are bought close together

Answer 7

They exert a repulsive force on each other and repel

Question 8

Why are most bodies neutrally charged?

Answer 8

They have an equal number of positive and negative charges

Question 9

Give an example of non contact force

Answer 9

Electromagnetic force,
Gravity

Question 10

What is an electric field

Answer 10

A region in which a charged object will experience a non contact electrical force.

Question 11

Where can electric fields be found

Answer 11

Surrounding any charged object

Question 12

Describe the electric field around a charged particle.

Answer 12

1. Strongest closest to object
2. Decreases in strength as you move away from object

Question 13

What happens to the force between two charged objects when they are moved closer together?

Answer 13

The force between them becomes strongs as the separation reduces

Question 14

In situations where sparks are unwanted what precaution must be taken to prevent the build up of static charge.

Answer 14

Any surfaces that are rubbing against each together should be earthed to allow the materials to discharge

Question 15

What is an electric current?

Answer 15

The flow of electrical charge

Question 16

State the equation charge

Answer 16

Charge= current x time
Columbs= amps x secs

Question 17

What can be said about the value of current at any point in a single closed loop?

Answer 17

Current is the same at all points in a closed loop

Question 18

What is a series circuit

Answer 18

A series circuit is one in which the same charge passes through all components, so the current through each component is the same

Question 19

What is a parellell circuit

Answer 19

A circuit in which the charge is split between branches

Question 20

What two factors does the current in a circuit depend on

Answer 20

1. Potential difference (V)
2. Resistance (R)

Question 21

What equation calculates p.d if current and resistance are known.

Answer 21

V= IR
Potential difference (V) = current (A) x resistance (ohms)

Question 22

What is ohms law

Answer 22

• Ohm’s Law relates voltage, current, and resistance in an electrical circuit.
• It states that the current flowing through a wire is directly proportional to the voltage and inversely proportional to the resistance.
• In simpler terms, more voltage means more current, but more resistance means less current.

Question 23

List 4 components for which resistance is not constant as current changes

Answer 23

1. Lamps
2. Diodes
3. Thermistors
4. LDR

Question 24

What happens to the resistance to a filiamant lamp as temperature increases? Why?

Answer 24

1. Resistance increases
2. Ions in metal has more energy, so it vibrates more, causing more collisions with electrons as they flow through the metal causing greater resistance

Question 25

What is diffrent about current flow through a diode?

Answer 25

1. The current only flows in one direction
2. Resistance is very high in the other direction preventing current flow

Question 26

State what happens to the resistance of a thermistor as temperature increases

Answer 26

The thermistors resistance decreases

Question 27

Give two examples of when a thermistor may be used

Answer 27

1. In a thermostat to turn a heater on below a certain temperature
2. In a freezer fo turn on a cooler when the temperature becomes too high

Question 28

State what happens to the resistance of a ldr as light intensity decreases

Answer 28

The ldrs resistance increases

Question 29

Give an application for an ldr

Answer 29

1. Street lamps or night lights
2. When light levels become low enough the light gains sufficient current to turn on

Question 30

What are two ways that a component can be connected in a circuit

Answer 30

1. Series (same loop)
2. Parallel (adjacent loop)

Question 31

How does the pd across two components vary when connected in series and parallel

Answer 31

1. Series- total pd is shared between each component.
2. Parallel- pd across each component is the same

Question 32

If two resistors are connected in parallel what can be said about their combined total resistance

Answer 32

The total resistance is less than the smallest of the two individual resistance

Question 33

Two resistors are connected in series what can be said about their total resistance

Answer 33

That total combined resistance is equal to the sum of the two individual resistances

Question 34

State two equations for the power of a circuit

Answer 34

1) Power = current x p.d
Watts= amps x volts
2) power= current^2 x Résistance
Watts= amps x ohms

Question 35

Energy transfered equation

Answer 35

Energy [joules] = power [watts] x time [secs]

Question 36

Energy transferrd 2

Answer 36

Energy (joules) = charge (columbs) x potential diffrence (volts)

Question 37

How should a volt metre be connected in a circuit

Answer 37

In parallel to the component that you are measuring the potential difference for

Question 38

How should an ammetre need to be connected in a circuit

Answer 38

In series with the brunch, you are measuring the current for