38 Electric circuit elements14 Give an expression for the equivalent capacitance of a number of
capacitors connected in series.
15 Can the current change suddenly in a capacitor?
16 Upon what factors does the inductance of an inductor depend?
17 Under what circumstances is the inductance of a coil variable?
18 Can the current through an inductor change suddenly?
19 Two coils of inductance 40 ~H and 10 ~H are placed such that there is a
coefficient of coupling of 0.8 between them. Determine the mutual
inductance between them.20 If the two coils of Question 19 were connected in series-aiding electrically,
what would be the effective inductance of the combination?
21 Explain the meaning of lumped parameters.
22 Give an expression for the energy stored in a capacitor in terms of its
capacitance and the potential difference across its plates.
23 Give an expression for the energy stored in an inductor in terms of its
inductance and the current passing through it.
24 Give an expression for the power dissipated in a resistor in terms of its
resistance and the current passing through it.
25 Give the relationship between energy and power.
2.8 PROBLEMS
1 Determine the equivalent resistance of four resistors connected in parallel
if their resistances are 1 1), 2 1), 2.5 1) and 10 1).
2 A 20 1) resistor is connected in series with a 40 1~ resistor and the
combination is connected in series with three 12 1~ resistors which are
connected in parallel. Determine the equivalent resistance of the whole
arrangement.
3 Calculate the resistance of a 200 m length of copper wire of diameter
1 mm. The resistivity of the copper is 0.0159 ~1~ m.
4 Two resistors (R1 = 5 1~ and R2 = 20 1)) are connected in series across a
100 V supply. Determine the voltage across R~.
5 If the two resistors in Problem 4 are connected in parallel across the same
supply, determine the current through R 2.
6 A battery has an open circuit terminal voltage of 24 V. When it supplies a