Electricity 2

Question 1

Transformers in National Grid

Answer 1

Transformers are used to change voltages and currents in transmission lines.

Question 2

As the power transferred must stay the same:

Answer 2

increasing voltage decreases current

decreasing voltage increases current

Question 3

Power

Answer 3

power = current(squared) × resistance

Question 4

To ensure that the minimum amount of power is lost from the cables:

Answer 4

the cables are thick so that their resistance is low

high voltages are used to reduce the current through the transmission lines

Question 5

Insulating materials

Answer 5

When insulating materials rub against each other, they may become electrically charged. Electrons, which are negatively charged, may be ‘rubbed off’ one material and on to the other. The material that gains electrons becomes negatively charged. The material that loses electrons is left with a positive charge.

Question 6

Electrical Fields

Answer 6

The direction of the arrow shows the way a positive charge will be pushed.

The closer together the arrows are, the stronger the field and the greater the force experienced by charges in that field.

This means that the field is stronger closer to the object.

Field lines point away from positive charges and towards negative charges.