NCEA Level 2 Physics
Electricity and electromagnetism
This page is designed to test your use of the equations for 91173 Electricity/electromagnetism standard.
Click on the Equation(s), Answer and Unit after each question to reveal the answers.
(There is a pdf of the questions on their own here and with answers here).
The formulae listed in the explanatory notes to the achievement standard will be provided, plus any other required formulae (e = 1.6 x 10^{19}C).
1. What is the resistance of a 240 V, 100 W light bulb?
Equation(s), Answer and Unit

576 
Ω 
2. Calculate the power dissipated in a 10 ohm resistor carrying a current of 1.2 A.
Equation(s), Answer and Unit

14.4 
W 
3. The starter motor of a car draws 200 A from a 12 V battery for 5 seconds. How much energy is produced in the 5 seconds?
Equation(s), Answer and Unit

12000 
J 
4. Calculate the total resistance in a circuit which consists of a 10 ohm, a 20 ohm and a 40 ohm resistor in parallel with each other.
Equation(s), Answer and Unit
5.7 
Ω 
5. Two resistors, 12 ohms and 24 ohms, are connected in series across a 9.0 V battery. Calculate the current flowing through the 12 ohm resistor.
Equation(s), Answer and Unit

0.25 
A 
6. Two points A and B are at different voltage levels. Calculate the potential difference between A and B if 16 J of work is done to move a 0.50 mC charge from A to B.
Equation(s), Answer and Unit
32000 
V 
7. A resistor of 10 ohms has a current of 2 Amps in it. What heat is being produced per second in the resistor?
Equation(s), Answer and Unit

40 
Js^{1} 
8. What power of electric fire can be connected to the 240 V mains supply if the maximum fuse value possible is 13 A?
Equation(s), Answer and Unit
3120 
W 
9. A 24 ohm resistor radiates 12 W. A 16 ohm resistor in parallel with it will radiate how much power?
Equation(s), Answer and Unit

18 
W 
10. An electron is moving through a magnetic field 410 ms^{1}. If the field has strength of 0.47 T, calculate the strength of magnetic force on it.
Equation(s), Answer and Unit
3.08 x 10^{17} 
N 
11. In an electron gun, the cathode and anode are separated by 1.3 cm and the potential difference between the two is 1000 V. Calculate the strength of the electric field between the cathode and the anode.
Equation(s), Answer and Unit
76923 
Vm^{1} 
12. The ionosphere is the top layer of Earth’s atmosphere. There is an electric potential difference of around 400 000 Volt between the ionosphere and the Earth’s surface. The height of the ionosphere as 200 km.
Calculate the energy transferred from the field when one electron travels from the ground to the ionosphere.
Equation(s), Answer and Unit

6.4 x 10^{14} 
J 
13. A power cable carries a 5.0A current between two pylons that are 450 metres apart. The Earth’s magnetic field in this region measures 5.5 X 10^{5}T and is at right angles to the power cables.
Calculate the magnetic force on the cable between the pylons.
Equation(s), Answer and Unit
0.12 
N 
14. The AIRBUS A380 airplane is the largest commercial jet ever. Its wingspan is 79.8m. The body and wings of the plane are made from electrically conducting material.
he AIRBUS A380 is flying over the north magnetic pole at 250ms^{1}.
Calculate the size of the induced voltage across the length of the wingspan when it is travelling over the north magnetic pole through a region where the Earth’s magnetic field is 7.0 x 10^{5} T.
Equation(s), Answer and Unit
1.40 
V 
15. Two parallel metal plates create an electric field of 100 Vm^{1}. An electron is fired from an electron gun into the space between the plates. Calculate the electric force acting on the electron anywhere between the charged plates.
Equation(s), Answer and Unit
1.6 x 10^{17} 
N 
16. A current of 0.1 A flows through a light bulb. Calculate the amount of charge that flows through the bulb in 45 minutes.
Equation(s), Answer and Unit
270 
C 
(Please note: There has been no attempt to show the correct number of significant figures in this exercise)