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13+ · Physics

CE.S-P2 Physics: Electricity, Magnetism and Waves

ISEB CE ISEB CE 13+ Science (Physics) · Calculator allowed · about 70 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

Which unit is used to measure electric current?

A) Volt
B) Ohm
C) Ampere
D) Watt

(Total for Question 1 is 1 mark)

Name the circuit component described by each definition below.

(a)A component that only allows current to flow through it in one direction, and gives out light when current flows through it.(1)

(b)A component whose resistance decreases as the light intensity shining on it increases.(1)

(Total for Question 2 is 2 marks)

A pupil sets up two circuits, each with one battery and two identical bulbs. In Circuit P, the two bulbs are connected one after another in a single loop. In Circuit Q, each bulb is connected directly across the battery, on its own separate loop.

(a)State whether Circuit P is a series circuit or a parallel circuit.(1)

(b)State whether Circuit Q is a series circuit or a parallel circuit.(1)

(c)One bulb is removed from each circuit. State what happens to the remaining bulb in Circuit P, and what happens to the remaining bulb in Circuit Q.(1)

(Total for Question 3 is 3 marks)

Two bar magnets are brought close together.

(a)State what happens when the north pole of one magnet is brought close to the north pole of the other.(1)

(b)State what happens when the north pole of one magnet is brought close to the south pole of the other.(1)

(Total for Question 4 is 2 marks)

Define each of the following terms used to describe waves.

(a)Wavelength(1)

(b)Frequency(1)

(c)Amplitude(1)

(Total for Question 5 is 3 marks)

A component in a circuit has a resistance of 15 ohm. A current of 0.4 A flows through it. Calculate the voltage across the component.

(Total for Question 6 is 2 marks)

Two resistors of 5 ohm and 7 ohm are connected in series in a circuit. A current of 2 A flows through the circuit.

(a)Calculate the total resistance of the circuit.(1)

(b)Calculate the voltage across the 7 ohm resistor.(2)

(c)Calculate the total voltage supplied by the battery.(1)

(Total for Question 7 is 4 marks)

Two resistors, 6 ohm and 3 ohm, are connected in parallel across a 12 V supply.

(a)Calculate the combined resistance of the parallel combination.(2)

(b)Calculate the total current supplied by the battery.(2)

(Total for Question 8 is 4 marks)

When a plastic rod is rubbed with a dry cloth, the rod becomes negatively charged. Explain, in terms of the movement of electrons, why this happens, and why the rod is then attracted to a wall.

(Total for Question 9 is 3 marks)

State three ways of increasing the strength of an electromagnet.

(Total for Question 10 is 3 marks)

A sound wave has a frequency of 500 Hz and a wavelength of 0.68 m. Calculate the speed of the sound wave.

(Total for Question 11 is 3 marks)

Priya shouts towards a distant cliff and hears the echo 3.0 s later. The speed of sound in air is 340 m/s.

(a)Calculate the total distance travelled by the sound wave (there and back).(2)

(b)Calculate the distance between Priya and the cliff, and explain why this is not the same as your answer to part (a).(2)

(Total for Question 12 is 4 marks)

A ray of light strikes a plane mirror.

(a)State the law of reflection.(1)

(b)The mirror is then rotated through 10 degrees while the incident ray stays in the same position. Calculate the angle through which the reflected ray turns.(2)

(Total for Question 13 is 3 marks)

A ray of light travels from air into a glass block, hitting the surface at an angle (not 90 degrees to the surface). Explain, in terms of the speed of light, why the ray changes direction as it enters the glass.

(Total for Question 14 is 3 marks)

An electric heater is rated at 2 kW and is switched on for 4 hours. It runs from the 230 V mains supply. Electricity costs 30p per kWh.

(a)Calculate the energy transferred by the heater, in kWh.(2)

(b)Calculate the cost of using the heater for this time.(2)

(c)Calculate the current drawn by the heater from the 230 V supply.(1)

(Total for Question 15 is 5 marks)

A circuit consists of a 4 ohm resistor connected in series with a parallel combination of a 6 ohm resistor and a 12 ohm resistor. The circuit is connected to a 24 V supply.

(a)Calculate the combined resistance of the parallel section.(2)

(b)Calculate the total resistance of the circuit.(1)

(c)Calculate the current supplied by the battery, and hence the voltage across the parallel section.(3)

(Total for Question 16 is 6 marks)

Describe how an electromagnet works, explain two ways of increasing its strength, and discuss one real-life application of an electromagnet.

(Total for Question 17 is 6 marks)

A student investigates how the length of a wire affects its resistance. She keeps the wire's diameter and material constant, and changes only the length, measuring the resistance with an ohmmeter each time. Assume the temperature of the wire also stays constant during the test.

(a)Identify the independent variable in this investigation.(1)

(b)Identify the dependent variable.(1)

(c)State one other variable, besides diameter, material and temperature, that the student should control to make this a fair test.(1)

(d)The student plots a graph of resistance (y-axis) against length (x-axis) and obtains a straight line through the origin. State what this shows about the relationship between resistance and length.(1)

(e)Using the graph, the student reads that a 2.0 m length of the wire has a resistance of 5.0 ohm. Predict the resistance of a 5.0 m length of the same wire.(2)

(f)One repeat reading for the 2.0 m wire gave a resistance of 8.0 ohm, much higher than the other repeat readings of about 5.0 ohm. Suggest one reason for this anomalous result.(1)

(Total for Question 18 is 7 marks)

A student investigates the current through a resistor for different potential differences (voltages) across it. Her results are shown below: V (V) = 1.0, 2.0, 3.0, 4.0, 5.0; I (A) = 0.20, 0.40, 0.60, 0.95, 1.00.

(a)State which of the five readings appears to be anomalous.(1)

(b)Suggest one reason why this reading might be anomalous, other than a simple reading or recording error.(1)

(c)Using the four readings that fit the pattern, describe the relationship between current and potential difference for this resistor.(1)

(d)Use the four non-anomalous readings to calculate the mean resistance of the resistor.(2)

(e)Explain how the student could improve the reliability of her results.(2)

(Total for Question 19 is 7 marks)

A shop compares two types of light bulb. For every 100 J of electrical energy supplied to each bulb: an old-style filament bulb usefully transfers 5 J as light (the rest is wasted as heat); a modern LED bulb usefully transfers 45 J as light (the rest is wasted as heat).

(a)Calculate the efficiency of the filament bulb.(1)

(b)Calculate the efficiency of the LED bulb.(1)

(c)Calculate how many times more efficient the LED bulb is than the filament bulb, and state which bulb is more efficient.(2)

(d)Suggest one reason, other than the cost of the bulb itself, why a school might choose to install LED bulbs across its site.(1)

(Total for Question 20 is 5 marks)

Mark scheme · CE.S-P2 Physics: Electricity, Magnetism and Waves

Question 1

B1 C) Ampere
Answer: C) Ampere

Question 2

(a) B1 LED (light-emitting diode), oe
(a) Answer: LED (light-emitting diode)
(b) B1 LDR (light-dependent resistor), oe
(b) Answer: LDR (light-dependent resistor)

Question 3

(a) B1 series
(a) Answer: Series
(b) B1 parallel
(b) Answer: Parallel
(c) B1 Circuit P: the remaining bulb goes out (the circuit is broken); Circuit Q: the remaining bulb stays lit (it still has a complete separate loop)
(c) Answer: Circuit P: the remaining bulb goes out. Circuit Q: the remaining bulb stays lit.

Question 4

(a) B1 they repel (push apart)
(a) Answer: They repel each other.
(b) B1 they attract (pull together)
(b) Answer: They attract each other.

Question 5

(a) B1 the distance from one point on a wave to the identical point on the next wave, e.g. crest to crest, oe
(a) Answer: The distance from one point on a wave to the identical point on the next wave (e.g. from one crest to the next crest).
(b) B1 the number of complete waves (oscillations) passing a point per second, measured in hertz (Hz)
(b) Answer: The number of complete waves passing a given point per second, measured in hertz (Hz).
(c) B1 the maximum displacement of a point on the wave from its undisturbed (rest) position
(c) Answer: The maximum displacement of a point on a wave from its undisturbed (rest) position.

Question 6

M1 correct substitution into V = I x R (0.4 x 15)
A1 V = 6 V, cao
Answer: 6 V

Question 7

(a) B1 R = 5 + 7 = 12 ohm
(a) Answer: 12 ohm
(b) M1 V = I x R = 2 x 7
(b) A1 14 V, cao
(b) Answer: 14 V
(c) B1 V = I x R(total) = 2 x 12 = 24 V, ft from (a)
(c) Answer: 24 V

Question 8

(a) M1 1/R = 1/6 + 1/3
(a) A1 R = 2 ohm, cao
(a) Answer: 2 ohm
(b) M1 I = V / R = 12 / 2
(b) A1 I = 6 A, cao
(b) Answer: 6 A

Question 9

B1 friction between the rod and the cloth transfers electrons, oe
B1 electrons move from the cloth onto the rod, so the rod gains extra electrons and becomes negatively charged
B1 the negatively charged rod induces an opposite (positive) charge on the surface of the wall, so the rod is attracted to that induced charge
Answer: Electrons transfer from the cloth to the rod during rubbing, giving the rod an overall negative charge; this charged rod then induces an opposite (positive) charge on the wall's surface, so the rod is attracted to the wall.

Question 10

B1 increase the current flowing through the coil
B1 increase the number of turns on the coil
B1 use (or improve) a soft iron core inside the coil
Answer: 1) Increase the current through the coil. 2) Increase the number of turns on the coil. 3) Use (or improve) a soft iron core inside the coil.

Question 11

M1 uses v = f x wavelength
M1 correct substitution, 500 x 0.68
A1 v = 340 m/s, allow awrt 340
Answer: 340 m/s

Question 12

(a) M1 distance = speed x time = 340 x 3.0
(a) A1 1020 m, cao
(a) Answer: 1020 m
(b) M1 divides total distance by 2 (1020 / 2)
(b) A1 510 m, with the explanation that the sound travels to the cliff AND back, so the one-way distance is half the total, ft from (a)
(b) Answer: 510 m

Question 13

(a) B1 the angle of incidence equals the angle of reflection, oe
(a) Answer: The angle of incidence equals the angle of reflection.
(b) M1 recognises the reflected ray turns through twice the angle the mirror is rotated
(b) A1 20 degrees (2 x 10), cao
(b) Answer: 20 degrees

Question 14

B1 light travels more slowly in glass than in air (glass is optically denser), oe
B1 because the ray meets the boundary at an angle, this change in speed causes the ray to change direction
B1 the ray bends towards the normal on entering the denser (glass) medium
Answer: Light slows down as it enters the glass (a denser medium); because the ray hits the boundary at an angle, this change of speed causes the ray to bend towards the normal - this is refraction.

Question 15

(a) M1 E = P x t = 2 x 4
(a) A1 8 kWh, cao
(a) Answer: 8 kWh
(b) M1 cost = 8 x 30p, ft from (a)
(b) A1 240p = GBP 2.40, cao
(b) Answer: GBP 2.40
(c) B1 I = P / V = 2000 / 230 = 8.7 A, allow awrt 8.7
(c) Answer: 8.7 A (2 s.f.)

Question 16

(a) M1 1/R = 1/6 + 1/12
(a) A1 R = 4 ohm, cao
(a) Answer: 4 ohm
(b) B1 R(total) = 4 (series) + 4 (parallel, ft from (a)) = 8 ohm
(b) Answer: 8 ohm
(c) M1 I = V / R(total) = 24 / 8, ft from (b)
(c) A1 I = 3 A
(c) A1 V(parallel) = I x R(parallel) = 3 x 4 = 12 V, ft from (a)
(c) Answer: I = 3 A, voltage across the parallel section = 12 V

Question 17

Level 1 (1-2): Basic, isolated statement(s) about electromagnets with little detail or scientific accuracy; the answer may be a simple list with no linking or explanation.
Level 2 (3-4): A generally correct description of how an electromagnet works and at least one correctly explained way of increasing its strength; any application given is only loosely linked to the physics.
Level 3 (5-6): A clear, logically ordered description of how an electromagnet works, at least two correctly explained ways of increasing its strength, and an accurate, well-linked real-life application.
Indicative content:
- A current flowing through a coil of wire produces a magnetic field.
- Placing a soft iron core inside the coil concentrates the field and magnetises the core, turning it into a magnet only while current flows.
- Switching off the current removes the magnetism almost immediately, unlike a permanent magnet.
- Increasing the current through the coil increases the strength of the electromagnet.
- Increasing the number of turns on the coil increases the strength of the electromagnet.
- Real-life applications include an electric bell, a scrapyard crane for lifting scrap metal, a relay switch or a loudspeaker; the answer should link the chosen application to the ability to switch the magnetism on and off, or to vary its strength.

Question 18

(a) B1 length of the wire
(a) Answer: Length of the wire
(b) B1 resistance of the wire
(b) Answer: Resistance of the wire
(c) B1 any one sensible control variable not already given, e.g. using the same type/make of wire for every length, using the same current for each test, or ensuring the ohmmeter connections are equally tight each time
(c) Answer: e.g. ensuring the connections to the ohmmeter are equally tight/consistent for every length tested.
(d) B1 resistance is directly proportional to length, oe
(d) Answer: Resistance is directly proportional to the length of the wire.
(e) M1 uses proportionality: scale factor = 5.0 / 2.0
(e) A1 12.5 ohm, cao
(e) Answer: 12.5 ohm
(f) B1 any one sensible suggestion, e.g. a poor/loose connection increased the contact resistance for that reading, the wire had heated up during that reading, or a measurement/misreading error
(f) Answer: e.g. a loose connection at the ohmmeter increased the measured resistance for that particular reading.

Question 19

(a) B1 the reading at V = 4.0 V (I = 0.95 A)
(a) Answer: V = 4.0 V, I = 0.95 A
(b) B1 any one sensible suggestion, e.g. the resistor heated up slightly, changing its resistance, or there was a brief fluctuation in the power supply
(b) Answer: e.g. the resistor may have heated up slightly during that reading, temporarily changing its resistance.
(c) B1 current is directly proportional to potential difference (a straight line through the origin); the resistor obeys Ohm's law, oe
(c) Answer: Current is directly proportional to potential difference (Ohmic behaviour).
(d) M1 calculates R = V / I for each of the four non-anomalous readings (all give 5.0 ohm)
(d) A1 mean resistance = 5.0 ohm, cao
(d) Answer: 5.0 ohm
(e) B1 repeat the reading at each voltage (e.g. 2-3 times)
(e) B1 calculate a mean current at each voltage, identifying and excluding any anomalous readings
(e) Answer: Repeat each voltage reading several times and calculate a mean current, checking for and excluding any anomalous results.

Question 20

(a) B1 efficiency = (5 / 100) x 100% = 5%
(a) Answer: 5%
(b) B1 efficiency = (45 / 100) x 100% = 45%
(b) Answer: 45%
(c) M1 45 / 5 (comparing the two efficiencies/useful outputs), ft from (a) and (b)
(c) A1 the LED bulb is more efficient, by a factor of 9
(c) Answer: The LED bulb is more efficient; it is 9 times more efficient than the filament bulb.
(d) B1 any one sensible reason, e.g. lower electricity bills over time, less wasted heat so rooms need less cooling, or a longer lifespan meaning fewer replacements
(d) Answer: e.g. lower running (electricity) costs over time, since much less energy is wasted as heat.

Physics: Electricity, Magnetism and Waves - Worksheets, Questions and Revision