Topic 2 - Electricity

Question 1

What is the equation that links power, potential difference and current?

Answer 1

Power = potential difference x current
P = VI

Question 2

What is the equation that links power, current and resistance?

Answer 2

Power = current^2 x resistance
P = I^2R

Question 3

What is the national grid?

Answer 3

The national grid is a system of cables and transformers that link power stations to consumers to transfer energy for domestic use.

Question 4

Why is the national grid an efficient way of transferring energy?

Answer 4

The national grid uses a high potential difference and low current. As potential difference is being increased, the current decreases which means that less energy is wasted because wires do not heat up as much so less thermal energy dissipates into the surroundings.

Question 5

What is the equation for transformers that link primary and secondary coils?

Answer 5

P.D in primary coil x current in primary coil = P.D in secondary coil x current in secondary coil

Question 6

What does a step up and step down transformer do?

Answer 6

A step up transformer increases potential difference which in turn decreases the current and vice versa for a step down transformer.

Question 7

What is the equation that links energy, charge and potential difference?

Answer 7

Energy transferred = charge flow x potential difference

E = QV

Question 8

What happens when insulating materials are rubbed against each other?

Answer 8

The negatively charged electrons are rubbed off one object and onto the other. The material which loses the electrons becomes postively charged and the object which gains the electrons become negatively charged. This causes a build up of static electricity.

Question 9

What causes sparking?

Answer 9

Sparking happens when electrical charges build up between object which increases potential difference. When the potential difference gets large enough, electrons have the ability to jump between objects which is known as a ‘spark’

Question 10

Explain attraction and repulsion in terms of their opposite and same charges.

Answer 10

Opposite charges attract and same charges repel. The forces get weaker with increased distance or could potentially make the objects move.

Question 11

What is formed around an electrically charged object? Explain in detail what is formed.

Answer 11

An electric field.

• – The closer to the charged object, the stronger the electric field.
• – The field lines go from positive to negative