AC CIRCUITS

The rms value of the complex voltage given by v = 16 sq.rt of 2 sin ωt + 12 sq.rt of 2 sin 3ωt is

• 2 sq.rt of 2 V

• 20 V

• 28 sq.rt of 2 V

• 192 V

A complex current wave is represented by the equation 1 = 5 + 5sin (120 π) t A. Find its average value in amperes

• 4.5

• 6

• 5

• 4

Three 10 ohm resistances are connected delta on a balanced three phase source. If the equation of the phase van = 120 sin ωt, what is the equation of the phase a line current?

• 36 sin ωt

• 13.15 sin (ωt - 30°)

• 11.22 sin (ωt + 30°)

• 11.88 sin (ωt – 56.56°)

When two capacitors of reactances 10 Ω and 20Ω are connected in parallel across a 100-volt supply, total VAR drawn will be

• 500

• 2

• 1500

• 15

A coil has a 50 Ω resistance and a 70Ω reactance. A capacitor is connected in parallel to produce resonance. The source voltage is 120 V. What is the power drawn by the circuit?

• 162 W

• 132 W

• 97 W

• 52 W

Determine the value of R for which power consumed in its maximum when it is connected in series with a coil of resistances 3 and reactance 20 across 230 V, 60 Hz ac supply

• 20 Ω

• 3 Ω

• 6.67 Ω

• 20.22 Ω

A circuit which has ω0 = 106 rad/sec, C = 10 pF and Q = 100, must have a resistance of __ kΩ.

• 10

• 5

• 1

• 100

What is the quality factor Q of an RLC series circuit having R = 5Ω, L = 10 mH and C = 100μF?

• 2

• 5

• 10

• 20

Impedance Z = 10 + j15 ohms and another impedance Z = 6 – j8 ohms are connected in parallel across a 60 Hz source. Find the total power in watts if total current is 15 A.

• 1845 W

• 2176 W

• 3188 W

• 2380 W

The current in a 4-ohm resistor is known to be 12 A with 60 degrees angle. Express the voltage across the resistor as a time function if the frequency of the current is 4 KHZ.

• v(t) = 48 cos (800 πt + 60°)v

• v(t) = 24 cos (800 πt + 30°)v

• v(t) = 48 cos (800 πt + 30°)v

• v(t) = 24 cos (800 πt + 60°)v