Advertisements
Advertisements
Question
A light bulb is rated at 120 W for a 220 V a.c. supply. Calculate the resistance of the bulb.
Advertisements
Solution
Power of the bulb, P = 120 W
Voltage, V = 240 V
The resistance of the buld is given as
`R = V^2/P = (240^2)/120 = 480 Omega`
APPEARS IN
RELATED QUESTIONS
Reactance of a coil is 157 Ω. On connecting the coil across a source of frequency 100 Hz, the current lags behind e.m.f. by 45°. The inductance of the coil is ...........
(a) 0·25 H
(b) 0·5 H
(c) 4 H
(d) 314H
A light bulb is rated at 100 W for a 220 V a.c. supply. Calculate the resistance of the bulb.
A light bulb is rated 100 W for 220 V ac supply of 50 Hz. Calculate
(i) The resistance of the bulb;
(ii) The rms current through the bulb.
An AC source is connected to a capacitor. Will the rms current increase, decrease or remain constant if a dielectric slab is inserted into the capacitor?
Which of the following plots may represent the reactance of a series LC combination?
The reactance of a circuit is zero. It is possible that the circuit contains
(a) an inductor and a capacitor
(b) an inductor but no capacitor
(c) a capacitor but no inductor
(d) neither an inductor nor a capacitor
(i) An alternating emf of 200 V, 50 Hz is applied to an L-R ciruit, having a resistance R of 10 Ω and an inductance L of 0.05H connected in series. Calculate :
(1) Impedance
(2) Current flowing in the circuit
(ii) Draw a labelled graph showing the variation of inductive reactance (`X_L`) verses frequency (`f`) .
A coil having self-inductance of 0.7 H and resistance of 165 Ω is connected to an a.c. source of
275V,50Hz. If π = `22/7`
Calculate:
(i) Reactance of the coil
(ii) Impedance of the coil ‘
(iii) Current flowing through the coil
The potential difference across the resistor is 160 V and that across the inductor is 120 V. Find the effective value of the applied voltage. If the effective current in the circuit is 1⋅0 A, calculate the total impedance of the circuit.
