exam questions i got wrong

Question 1

A fault causes the live wire to make an electrical connection with the metal case of the
washing machine.
The earth wire is not connected to the metal case of the washing machine.
Explain why it would not be safe for a person to touch the metal case.

Answer 1

the person could get an electric
shock
because there is a current in the
person

Question 2

The earth wire is now connected to the metal case of the washing machine.

Explain why it would now be safe for a person to touch the metal case, even if the live wire touches the metal case.

Answer 2

the charge flows through the
earth wire (instead of the
person)
because the resistance of the
earth wire is much less than that
of a person

Question 3

properties of alpha

Answer 3

• an alpha particle is the same as a helium nucleus
• alpha is the least penetrating
• alpha is stopped by paper or skin
• alpha has the shortest range in air
• alpha will travel a few cm in air
• because alpha is most ionising
• because alpha has a charge of +2

Question 4

properties of beta

Answer 4

a beta particle is an electron (emitted from the nucleus)
* beta penetrates less than gamma and more than alpha
* beta is stopped by a thin sheet of aluminium
* beta has a shorter range than gamma
* beta will travel up to 1m in air
* because beta is more ionising that gamma and less ionising
than alpha
* because beta has a charge of -1

Question 5

properties of gamma

Answer 5

gamma radiation is an electromagnetic wave
* gamma is the most penetrating
* gamma is reduced/stopped by several cm of lead or thick
concrete
* gamma has the largest range in air
* gamma will travel very large distances in air
* because gamma is least ionising
* because is uncharged

Question 6

Explain why the student needed to adjust the variable resistor each time she changed
the length of the wire.

Answer 6

(the variable resistor) changes
the resistance of the circuit
to keep the current the same
so the temperature of the wire is
kept constant

Question 7

what type of fuel is wood?

Answer 7

a renewable biofuel

Question 8

Give two environmental effects of using wood as an energy resource.

Answer 8

burning wood causes air
pollution
* burning wood may lead to deforestation
* destruction of habitats
* burning wood is carbonneutral

Question 9

Describe the change to the stores of energy of the wood as water is heated

Answer 9

the chemical store of energy of
the wood decreases

Question 10

Describe the change to the stores of energy of the pipe as water is heated

Answer 10

the internal/thermal store of
energy of the pipe increases

Question 11

Describe the change to the stores of energy of the water as water is heated

Answer 11

the internal/thermal store of
energy of the water increases

Question 12

The temperature of the water reaches 42 °C
The temperature then stays constant even though the fire continues to burn.
Explain why the temperature of the water stays constant.

Answer 12

energy is dissipated (to the
surroundings)
at the same rate that energy is
transferred to the water

Question 13

metal

Answer 13

has a high thermal
conductivity
which increases the rate of
energy transfer from the mixture

Question 14

plastic

Answer 14

has a low thermal
conductivity
which reduces the rate of
energy transfer from the
surroundings (to the liquid
coolant at –20°C)

Question 15

The liquid coolant has a freezing point below –20 °C
Explain one other property that the liquid coolant should have.

Answer 15

a high specific heat capacity
so it can absorb a large amount
of energy with only a small
temperature change

Question 16

Each leg of a kangaroo has a tendon connected to a muscle. Each tendon can be
modelled as a spring.
When a jumping kangaroo lands on the ground, the tendons stretch.
Explain why a kangaroo can jump higher as its speed increases

Answer 16

the (maximum tendon)
extension increases (as speed
increases)
so the elastic potential energy
increases
which is transferred to
gravitational potential energy