Physics Y7 & Y8 Electricity

Question 1

How do you calculate the resistance of a resistor?

Answer 1

Resistance = Voltage/Current

Question 2

What are the two types of charge and how do you make insulating materials become charged?

Answer 2

There are two types of charge, positive and negative. You can make a plastic rod charged by rubbing it with a cloth.

Question 3

Why does a light bulb transfer energy to its surroundings?

Answer 3

A bulb transfers energy to the surroundings by light waves and heating when a current flows through it because the filament wire gets hot.

Question 4

What is the structure of an atom?

Answer 4

An atom is made of a tiny central nucleus (made up of neutrons and protons) surrounded by electrons which orbit it. There are the same number of protons and electrons in an atom. The atom has no overall charge.

Question 5

Why does a light bulb get hot when a current flows through it?

Answer 5

It gets hot because electrons collide with the atoms inside the filament wire. This is because the filament wire has resistance. This is called resistive heating.

Question 6

Why are resistors useful components in electric circuits?

Answer 6

A resistor can be used to keep the current at safe levels in a circuit and also to make heating devices e.g. a kettle. Energy is transferred in the same way as in a bulb, so it gets hot.

Question 7

How is voltage measured? What does the measurement tell you?

Answer 7

Voltage is measured using a voltmeter, its unit is volts. The voltage is the energy transferred to the component by the electrons or by the battery to the electrons. higher voltage = more energy transferred.

Question 8

Why does rubbing a plastic rod with a cloth cause it to become charged?

Answer 8

The movement of electrons is responsible for charging the rods; electrons are added (becomes negative) or taken away (becomes positive) by the friction between the cloth and the rod.

Question 9

What is voltage?

Answer 9

Voltage is a measure of the energy transferred to (or from) the electrons flowing in the circuit.

Question 10

What happens if we keep on charging up an object?

Answer 10

If we charge an object up negatively by continually adding electrons to it, there comes a point where the electrons won’t stay on the object and will jump off of it directly down to the ground or to another object that is touching the ground. We see this movement of electrons as a spark.

Question 11

How does the voltage across the battery relate to the voltage across the components in a series circuit?

Answer 11

The voltage across the battery equals the total voltage of all of the components. This is because the energy transferred to the electrons as they pass through the battery must equal the work done.

Question 12

How do electric shocks happen?

Answer 12

If electrons flow from a very charged object to the ground through a person they will experience an electric shock.

Question 13

What would the current voltage graph look like for a resistor?

Answer 13

It would be a straight line through the origin since resistor voltage is directly proportional to current.

Question 14

What is an electrical current?

Answer 14

The movement of charged particles such as electrons is known as an electric current.

Question 15

What would the current voltage graph look like for different resistors?

Answer 15

The larger the resistor, the more voltage required to push the same amount of current through it.

Question 16

How can you make an electrical current flow in a circuit?

Answer 16

We can make electrons in the wires move by attaching a battery across a wire. The electrons move in the circuit because they are being pushed away from the negative terminal and are being attracted to the positive terminal of the battery.

Question 17

What is resistance measured in?

Answer 17

Resistance is measured in ohms (Ω)

Question 18

Why are wires in circuits made out of metals?

Answer 18

Metals are conductors because the electrons are free to move – some electrons don’t belong to any one particular atom like they do in insulators. The forces exerted on electrons from a typical battery are not enough to make them move in an insulator because they are very securely attached to an individual atom.

Question 19

What energy transfers take place in a circuit and how quickly does it happen?

Answer 19

In a simple battery/bulb circuit when a current flows the chemical store of the battery decreases and the thermal store of the bulb increases. This energy transfer happens as soon as the circuit is completed.

Question 20

How do you measure current and what is it you are actually measuring when you do so?

Answer 20

We measure current using an ammeter. When we measure current we are measuring of the rate of flow of electrons.

Question 21

What is the unit for current and what does it mean?

Answer 21

Current is measured in amperes (amps, A) and 1A is the equivalent of more than 6 trillion electrons flowing past a point in the circuit each second!

Question 22

What is a series circuit?

Answer 22

A series circuit is a simple circuit where there is only one route that electrons could take from the battery, through all the components, and back to the battery.

Question 23

Does current change depending on where you measure it in a series circuit?

Answer 23

Current is the same everywhere in a series circuit.

Question 24

What happens to current when a larger battery voltage is used?

Answer 24

Current increases when the battery voltage is increased. This is because the electrons experience stronger forces of attraction and repulsion to the terminals.

Question 25

What is resistance?

Answer 25

Resistance is a measure of how difficult it is for electrons to move through a circuit.

Question 26

Why does a bulb get brighter when there is a larger current flowing through it?

Answer 26

A larger current increases the rate at which energy is transferred from the battery to the bulb. The bulb develops more power when a larger current flows through it.

Question 27

What is an electromagnet?

Answer 27

If a wire is wrapped around an iron core, connected to a battery, and then switched on a magnetic field is created. This arrangement is known as a solenoid.

Question 27

How do you increase the strength of an
electromagnet?

Answer 27

If you have more turns of wire wrapped round the iron core and if you increase the current flowing through the wire you will increase the strength of the electromagnet.