Alternating current
Q.1 The electric mains in a house are marked 220 V 50 Hz write down the equation for an instantaneous voltage. v= 311 sin (100 πt)
Q.2 The peak value of an alternating voltage applied to a 50 om resistance is 10 V find the RMS current. Ans. 141.4mA
Q.3 if the effective value of current in 50 Hz AC circuit is 5MP are what is the peak value of current, the mean value of current over a half cycle and the value of current 1/300 s after it was zero. Ans . i0 = 5 root2 , iavg= 10 root2/ π, 5 root 3/2
Q.4 The peak value of an alternating current of frequency 50 Hz is 14.14A. Find its RMS value how much time will the current take in reaching from 0 to maximum value. Ans. Irms= 10A, t= 5ms.
Q.5 For i= 50 sin100 πt. Calculate a) mean value of AC over positive half cycle b) RMS value of current. Ans. Iavg= 31.8A. c) irms= 35.35 A
Q.6 A voltage E=60 sin(314t), is applied across a resistor of 20 ohm. What will be the reading of a) hot wire ammeter b) ordinary moving coil ammeter. Ans. Irms= 2.121A , 0
Q.7 The electric current in a circuit is given by i= i0(t/ tau) for some time. Calculate the RMS current for the period t=0 to t=tau Ans i0/root3
Q.8 A coil of resistance 300 ohm and inductance 1.0 Henry is connected across an alternating voltage of frequency 300/2 π . Calculate the phase difference between voltage and current in the circuit. Ans 45°
Q.9 R= 3 ohm , L = 0.4H and ε = 20sin10t calculate- inductive reactance xL, Impedance Z, phase difference phi, Peak current i0, instantaneous current i, instantaneous voltage in Resistance VR and instantaneous voltage in Inductance VL.
Q.10 The potential difference across the resistor is 160 V and that across the inductor is 120 V the effective current in the circuit be 10A , calculate the impedance of the circuit in ohm.
Q.11 If R = 3 ohm, C= 25 µF, ε = 10sin(10^4t) calculate- capacitive reactance Xc, impedance Z, phase difference phi, peak current i0, Instantaneous current i, ins. Voltage in resistance VR, Instantaneous Voltage in Capacitor VL.
Q.12 L = 0.16H, R= 3 ohm, C= 500 µF, V= 20sin100t. Calculate- XL, Xc, Z, phi, i0, i(t), VR(t), VL(t), Vc(t) and Pavg.
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