LEVEL 7:
28. John connects up the circuit shown below.
The bulb is not bright enough. His friend suggests four circuits which could be used to make the bulb brighter.
(a) Which is the correct circuit to use: A, B, C or D? A B C D 1 mark
Next John sets up circuit E and notes the reading on the ammeter.
He then places another bulb in the circuit, to make circuit F. He notes the ammeter reading in circuit F.
(b) How will the ammeter reading in circuit F compare with that in circuit E?
The reading in F is .
1 mark
Explain you answer.
(c) Draw a circuit diagram in which two bulbs are lit as brightly as the bulb in circuit E, and the ammeter reading is the same as in circuit E.
29. Alison has a car. The part of each tyre in contact with the road is flattened. This is shown in the diagram.
(a) When Alison gets into the car, the force on each tyre increases. What happens to the area of tyre in contact with the road?
(b) There is a leak of air from one of the tyres, and the air pressure in the tyre falls. What happens to the area of the tyre in contact with the road?
(c) The weight of the car is 8400 N. Each tyre supports a weight of 2100 N. The pressure exerted by each tyre on the road is 20 N/cm2. Calculate the area of each tyre in contact with the road.
cm2 1 mark
Alison goes for a drive on three different days.
(d) Write the missing values in the table.
3 marks
(e) Explain why the calculated car speeds are averages.
30. A white box of photographic paper has written on it, in large red letters:
(a) The box of paper is in a photographic darkroom where the only light is from a red lamp.
(i) What colour does the white box appear? 1 mark
(ii) What colour does the red writing appear? 1 mark
(b) The red lamp is now switched off and a green lamp is switched on.
(i) What colour does the red writing appear in green light?
(ii) Explain why the writing appears to be this colour.
31. Circuit breakers are switches which open when the current becomes too large. The diagram shows a simple circuit breaker. The springy piece of metal pushes down on the iron rocker, and this holds the switch contacts together.
(a) (i) There is a current in the coil in the circuit breaker. What is the purpose of the coil?
(ii) What is the purpose of the soft iron core in the coil? 1 mark
(b) Give two properties of iron which make it a good choice of material for the rocker.
1.
2
2 marks
(c) The diagram below shows the circuit breaker with the switch contacts open.
Why do the switch contacts separate when the current becomes too large?
32. A pupil fixes a small electromagnet close to a thin springy steel sheet. The device acts like a small speaker. She connects a battery and switch to the electromagnet as shown.
(a) (i) When the pupil closes the switch, what will happen to the steel sheet? 1 mark
(ii) The pupil opens the switch again. What will happen to the steel sheet now? 1 mark
(iii) If the pupil had connected the battery the other way round, what difference would this have made to your answer to part (i)? 1 mark
(b) The pupil removes the battery and switch. She connects the electromagnet to a power supply which switches the current on and off 1000 times each second. The steel sheet vibrates and makes a sound.
(i) She then adjusts the power supply so that the current is switched on and off 3000 times each second.
What difference does this make to the pitch of the sound?
Give a reason for your answer. 2 marks
(ii) The pupil now adjusts the power supply so that the current is larger. Explain why this makes the sound louder. 1 mark
33. (a) The ‘two second rule’ is a rule for car drivers. The rule is as follows:
‘Leave enough space between you and the vehicle in front so that you can pull up safely if it suddenly slows down or stops. . . A two second time gap may be sufficient. . . Use stationary objects (eg lampposts) to help you keep a two second gap.’ (The Highway Code, 1993)
(i) The traffic is moving at 20 m/s, and a driver is keeping to the ‘two second rule’. What is the distance between the driver and the car in front?
(ii) The traffic increases its speed to 25 m/s, but the driver stays the same distance from the car in front. She sees the car in front pass a lamp post. How long will it take her to reach the same lamp post? s
(b) The driver decides to check her speedometer while driving along a motorway. She measures how long it takes her to travel 6 km. It takes her exactly 4 minutes. What was her speed in km/h? Show your working.
km/h
34.
(a) Each of the four objects shown above started at room temperature. Now they are all at different temperatures, as described by the labels.
(i) Which object is at the highest temperature? . 1 mark
(ii) Which object has lost thermal energy? 1 mark
(iii) Which object has had the largest gain in thermal energy?
(b) Omar puts a hot steel ball into a beaker of cold water. He waits until the temperatures of the ball and the water are the same.
From his results, he calculates that:
the thermal energy stored in the steel ball has fallen by 3770 J; the thermal energy stored in the water has risen by 2940 J.
The energy stored in the water rose by less than 3770 J. What has happened to the other 830 J? 1 mark
35. Gareth is trying to release a nut with a spanner. The diagram shows the size of the force he is exerting and where this force acts on the handle.
(a) The spanner applies a moment, or turning effect, to the nut. Calculate the size of this moment or turning effect. Give the units.
(b) Give two ways in which Gareth could increase the moment he applies using this spanner.
1 2 2 marks
1
2 2 marks
36.
A bell in a church tower is attached to a wheel of radius 0.8 m. The bell is balanced upside down. The bellringer pulls the rope with a force of 50 N.
(a) Calculate the moment (turning effect) on the wheel. Give the unit. 2 marks
(b) The bell turns. When the rope is travelling at its highest speed, it moves 0.5 m in 0.04 s. What speed is this? Give the unit. 2 marks
(c) The bell rings twice but the second ring is quieter than the first. Both rings have the same pitch.
Complete the sentences below to compare the two rings.
The amplitude of the second ring was the amplitude of the first ring.
The frequency of the second ring was frequency of the first ring. 2 marks
(d) The sound of a bell is within the audible range of most people.
Which is most likely to be the frequency of the sound made by a bell? Tick the correct box.
(e) The energy given out when the bell rings was originally stored in the bellringer. Describe the main sequence of useful energy transfers which take place when a bellringer rings a church bell. 3 marks
37. The diagram shows an electromagnetic relay. The relay is connected in a circuit with a battery, a lamp and a switch.
(a) (i) Give the name of a suitable material to use for the core of the electromagnet.
(ii) Give the name of a suitable material to use for the armature.
(b) (i) Explain why the contacts come together when the switch is closed.
(ii) When the switch is now opened, the bulb stays on. Explain why.
38. A pupil has two well insulated containers of water at 20° C. She takes two identical blocks of aluminium, both at 100° C, and puts one into container A and the other into container B. The temperature of the water rises in each container until it reaches a steady value. Her results are shown in the table.
(a) Explain why the final temperature of the water is lower in container B.
(b) What is the final temperature of each aluminium block?
The block in container A is at ° C.
The block in container B is at °C.
(c)
Which of the identical aluminium blocks transferred more energy to the water? Explain your reasoning. 1 mark
Which of the identical aluminium blocks transferred more energy to the water? Explain your reasoning.