FACULTY OF APPLIED SCIENCE
DEPARTMENT OF MATHEMATICS AND PHYSICS
WEEK 18 ELECTRICITY TUTORIAL TOTAL: 80 MARKS
QUESTION 1 (30 MARKS)
a. State Ohm’s law. (2)
b. Differentiate between current and conventional current. (4)
c. Differentiate between conductivity and resistivity. (4)
d. Differentiate between electric cell and battery. (4)
e. Differentiate between Ohmic and non-Ohmic conductors. (4)
f. What is meant by the following terms?
i) Current density; (2)
ii) Potential difference. (2)
g. Name FOUR factors that affect resistance. (4)
h. Give TWO examples of non-Ohmic devices. (2)
i. Briefly explain why colour coding is often used on resisters? (2)
QUESTION 2 (50 MARKS)
a. Use table 2 of colour coding for resistors to specify the colour coding of the following 3-band resistors:
i) A 5 kΩ, tolerance ± 5%; (3)
ii) A 20 kΩ, tolerance ± 10%. (3)
b. A 2.2 Ω resistor is connected across a 9 volt battery. The voltage between the terminals of the battery
is observed to be only 8.30 V. Find the internal resistance of the battery. (4)
c. A battery has an electromotive force of 12 V and internal resistance of 0.050 Ω. Its terminals are
connected to a load resistance of 3 Ω. Find:
i) The current in the circuit; (2)
ii) The terminal voltage; (2)
iii) The total power delivered by the battery. (2)
d. A 500 mm long piece of wire with a diameter of 1 mm has a resistance of 10. 7 mΩ.
i) Calculate the resistivity of the wire; (3)
ii) Determine the new resistance of the wire if it drawn out uniformly until it has a diameter of 200 µm.
(2)
e. A car headlight filament is made of tungsten and has a cold resistance of 0.35 Ω. If the filament is
cylinder 4 cm long (it may be coiled to save space), what is its diameter? (4)
DEPARTMENT OF MATHEMATICS AND PHYSICS
WEEK 18 ELECTRICITY TUTORIAL TOTAL: 80 MARKS
QUESTION 1 (30 MARKS)
a. State Ohm’s law. (2)
b. Differentiate between current and conventional current. (4)
c. Differentiate between conductivity and resistivity. (4)
d. Differentiate between electric cell and battery. (4)
e. Differentiate between Ohmic and non-Ohmic conductors. (4)
f. What is meant by the following terms?
i) Current density; (2)
ii) Potential difference. (2)
g. Name FOUR factors that affect resistance. (4)
h. Give TWO examples of non-Ohmic devices. (2)
i. Briefly explain why colour coding is often used on resisters? (2)
QUESTION 2 (50 MARKS)
a. Use table 2 of colour coding for resistors to specify the colour coding of the following 3-band resistors:
i) A 5 kΩ, tolerance ± 5%; (3)
ii) A 20 kΩ, tolerance ± 10%. (3)
b. A 2.2 Ω resistor is connected across a 9 volt battery. The voltage between the terminals of the battery
is observed to be only 8.30 V. Find the internal resistance of the battery. (4)
c. A battery has an electromotive force of 12 V and internal resistance of 0.050 Ω. Its terminals are
connected to a load resistance of 3 Ω. Find:
i) The current in the circuit; (2)
ii) The terminal voltage; (2)
iii) The total power delivered by the battery. (2)
d. A 500 mm long piece of wire with a diameter of 1 mm has a resistance of 10. 7 mΩ.
i) Calculate the resistivity of the wire; (3)
ii) Determine the new resistance of the wire if it drawn out uniformly until it has a diameter of 200 µm.
(2)
e. A car headlight filament is made of tungsten and has a cold resistance of 0.35 Ω. If the filament is
cylinder 4 cm long (it may be coiled to save space), what is its diameter? (4)
