ElectricityIB MYP Physics: Topic test

20 questions, 54 marks

IB MYP Physics

Electricity topic test

Total 54 marks

Name

Class

Date

1
A tall building in Hong Kong has a metal spike on its roof, joined to the ground by a thick copper strip. During a thunderstorm, parts of the clouds become charged by friction between ice crystals and water droplets.
(a)
Which particles move from one material to the other when objects become charged by friction?
[1 mark]
AProtons
BNeutrons
CWhole atoms
DElectrons
(b)
Two charged regions of cloud attract each other. Which statement must be true?
[1 mark]
ABoth carry positive charge
BThey carry opposite charges
CBoth carry negative charge
DThey carry no charge
(c)
Explain why a copper strip, and not a plastic strip, is used to join the spike to the ground.
[2 marks]
Total for question 1: 4 marks
2
A power bank in Seoul charges a phone with a steady current of 0.50 A for 2.0 hours. The potential difference across the phone's charging cable is 5.0 V.
(a)
How much charge flows through the cable?
[1 mark]
A3600 C
B1.0 C
C0.25 C
D60 C
(b)
What does a potential difference of 5.0 V mean?
[1 mark]
A5.0 coulombs of charge pass for every joule of energy
BA current of 5.0 A flows
C5.0 joules of energy are transferred for every coulomb of charge
D5.0 joules of energy are transferred every second
(c)
State how an ammeter and a voltmeter should be connected to measure the current in the cable and the potential difference across the phone.
[2 marks]
Total for question 2: 4 marks
3
An electrician in Bogotá compares three copper wires for a new circuit. Wire A is 2.0 m long with a cross-sectional area of 1.0 mm². Wire B is 4.0 m long with a cross-sectional area of 1.0 mm². Wire C is 2.0 m long with a cross-sectional area of 2.0 mm².
(a)
Put the three wires in order of resistance, lowest first, and explain your order.
[3 marks]
(b)
Wire A is connected to a 0.60 V supply and carries a current of 12 A. Calculate its resistance. Wire B has twice the resistance of wire A. Calculate the current in wire B when it is connected to the same supply.
[4 marks]
Total for question 3: 7 marks
4
An electric shower in Johannesburg is rated at 7.5 kW when connected to the 230 V mains supply. A family uses it for 10 minutes each morning. Electricity costs USD 0.18 per kWh.
(a)
Calculate the current in the shower, its resistance and the cost of one 10-minute shower.
[6 marks]
(b)
A solar water heater would cost USD 1200 to install and would cut the electricity the family uses for showers by 80%. Discuss whether the family should install it.
[6 marks]
Total for question 4: 12 marks
5
A string of festive lights in Mexico City has 20 identical bulbs connected in series. The string is plugged into a 240 V supply.
(a)
What is the potential difference across each bulb?
[1 mark]
A240 V
B12 V
C4800 V
D0.083 V
(b)
One bulb breaks and its filament snaps. What happens?
[1 mark]
AOnly that bulb goes out
BThe other bulbs get brighter
CThe other bulbs stay lit but are dimmer
DAll the bulbs go out
(c)
State two advantages of wiring the bulbs in parallel instead of in series.
[2 marks]
Total for question 5: 4 marks
6
A student in Auckland fits a three-pin plug to the cable of a table lamp that has a metal base. The lamp is rated at 60 W and is used on a 230 V a.c. mains supply.
(a)
Which wire should be connected to the live pin?
[1 mark]
AThe blue wire
BThe green and yellow wire
CThe brown wire
DAny of the three wires
(b)
Which fuse is the best choice for the lamp?
[1 mark]
A3 A
B0.2 A
C13 A
D30 A
(c)
Explain how the earth wire protects the user if the live wire touches the metal base of the lamp.
[2 marks]
Total for question 6: 4 marks
7
A student in Cape Town tests a thermistor for a fire alarm. She measures its resistance at four temperatures: 5000 Ω at 20 °C, 2500 Ω at 40 °C, 1200 Ω at 60 °C and 600 Ω at 80 °C.
(a)
Describe the pattern in the data and state a conclusion about how the resistance of the thermistor depends on temperature.
[3 marks]
(b)
The thermistor is connected in series with a 6.0 V cell and an ammeter. Calculate the current at 60 °C. Explain how the current changes in a fire and how this could be used to sound an alarm.
[4 marks]
Total for question 7: 7 marks
8
A cement factory in Pune fits an electrostatic precipitator to its chimney. Smoke containing tiny dust particles passes between rows of wires and plates. The wires are connected to a very high negative voltage and the plates are connected to earth.
(a)
Explain how the precipitator removes dust from the smoke.
[6 marks]
(b)
The precipitator uses 150 kW of power and runs 24 hours a day. Electricity costs USD 0.12 per kWh. Discuss whether the factory should install it.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).