Past Paper Mistakes

Question 1

In addition to power input, light bulbs should also be labelled with the rate at which
they emit visible light.

Suggest why.

Answer 1

Bulbs also transfer thermal
energy

the efficiency of the light bulb
also needs to be considered

Question 2

A student rubbed a plastic rod with a cloth.

The rod became negatively charged and the cloth became positively charged.

Explain why the cloth became negatively charged.

Answer 2

electrons transferred from the
cloth (to the rod)

electrons are negatively charged

(so) there are more positive
charges than negative charges
on the cloth

Question 3

A negatively charged rod is held near an earthed conductor.

Explain why a spark jumps between the negatively charged rod and the earthed
conductor.

Answer 3

the (large) potential difference
between the two objects

(causes negative) electrons /
charges to move (through the air)

(from the rod) to the conductor

Question 4

The total power output of the girl was greater than the answer to question 09.1.

Suggest two reasons why.

Answer 4

some energy is wasted in her
muscles

girl increases her kinetic energy
(as well as increasing her
gravitational potential energy

Question 5

Suggest two reasons why wind power was not able to meet this demand.

Answer 5

It was not windy.

There are not enough wind
turbines (in the UK)

Question 6

Explain why people should be encouraged to use energy efficient electrical devices.

Answer 6

More efficient devices waste less energy.

So less fossil fuels burned so less environmental impact.

Question 7

Thermometer A is more likely to be misread.

Give one reason why.

Answer 7

viewing angle affects
measurement
or
parallax error

allow judgement needed in
reading the position (of the liquid
in the thermometer)

allow the level of the liquid may
be between lines

allow number of lines may be
miscounted