Download 1E6_Tutorial 5

1E6 Tutorial 5
Problem 1
(a) Explain what you mean by the time constant of a circuit that includes a resistor and
capacitor connected in series
(b) A 100 F capacitor is connected in series with a 8 k resistor. Determine
(i) time constant of the circuit
If the combination is connected to a 100 V supply, find
(ii) the initial rate of rise of voltage across the capacitor,
(iii) the initial charging current,
(iv) the ultimate charge in the capacitor; and
(v) the ultimate energy stored in the capacitor.
Problem 2
Explain what is meant by the terms: electric field strength, electric flux density and the
relative permittivity and give the units of these terms
A capacitor consists of two metal plates, each 600 mm x 500 mm, spaced 1 mm apart.
The space between the metal plates is occupied by a dielectric having a relative
permittivity of 6, and a potential difference of 3 kV is maintained between the plates.
Calculate: (i) the capacitance in pico Farads (ii) the electric field strength and (iii) the
electric flux density in the dielectric.
Problem 3
Explain the term time constant in connection with an inductive circuit
A coil having a resistance of 25  and inductance of 2.5 H is connected across a 50 V d.c.
supply. Determine
(i)
(ii)
(iii)
the initial rate of growth of the current;
the value of the current after 0.10 s; and
the time required for the current to grow to 1.8 A.