Question 11
(a) What is an electric field?(b) State two differences between gravitational potential and gravitational field strength.
(c) Study the circuit diagram below and answer the questions that follow.
Calculate the:
(i) equivalent capacitance;
(ii) total energy stored.
(d) An alternating voltage V = 25 sin 100 πt is applied to a pure capacitive circuit. If the maximum current in the circuit is 20 mA, calculate the:
(i) capacitive reactance;
(ii) capacitance of the capacitor.
(e) What is a phasor diagram?
Observation
Part (a): Candidates performance was below average.
Part (b): Candidates performance was below average.
Part (c) Performance was fair. Many candidates correctly
Part (d): Performance was fair. Most candidates were unable to explain the phasor diagram.
The expected answer is :
A region/space around a charged particle/body where electric force is experienced/felt.
(b) Differences between gravitational potential and gravitational field strength
Gravitational potential |
Gravitational field strength |
Work done per unit mass |
Force per unit mass |
Obeys the inverse law |
Obeys the inverse square law |
Unit is J kg-1/V |
Unit is N kg-1/Vm-1 |
It is a scalar quantity |
It is a vector quantity |
(ci) Calculation of equivalent capacitance
(ii) Calculation of total energy stored
(di) Calculation of capacitive reactance 
(ii) Calculation of capacitance of capacitor
(e) Phasor diagramA vector diagram showing the relationship between the current and voltage and the phase difference between them.