An ac source of variable frequency \(f\) is connected to an \(LCR\) series circuit. Which of the following graphs represents the variation of the current \(I\) in the circuit with frequency \(f\)?
1. | 2. | ||
3. | 4. |
A step–down transformer transforms a supply line voltage of 2200 volt into 220 volt. The primary coil has 5000 turns. The efficiency and power transmitted by the transformer are 90% and 8 kilowatts respectively. How many turns are there in the secondary one?
1. | 5000 | 2. | 50 |
3. | 500 | 4. | 5 |
The power factor of the given circuit is:
1. | \(1 \over 2\) | 2. | \(1 \over \sqrt2\) |
3. | \(\sqrt3 \over 2\) | 4. | \(0\) |
1. | \(V_r=V_L>V_C\) |
2. | \(V_R \neq V_L=V_C\) |
3. | \(V_R \neq V_L \neq V_C\) |
4. | \(V_R=V_C \neq V_L\) |
In a box Z of unknown elements (L or R or any other combination), an ac voltage is applied and the current in the circuit is found to be . The unknown elements in the box could be:
1. | Only the capacitor |
2. | Inductor and resistor both |
3. | Either capacitor, resistor, and an inductor or only capacitor and resistor |
4. | Only the resistor |
What is the average power dissipated in the ac circuit if current i = 100sin100t A and V=100sin(100t+π/3) volts?
1. 2500 W
2. 250 W
3. 5000 W
4. 4000 W
The circuit is in a steady state when the key is at position 1. If the switch is changed from position 1 to position 2, then the steady current in the circuit will be:
1. \(E_o \over R\)
2. \(E_o \over 3R\)
3. \(E_o \over 2R\)
4. \(E_o \over 4R\)
In an \(LCR\) circuit having \(L = 8.0~\text{H}\), \(C= 0.5~\mu\text{F}\) and \(R = 100~\Omega\) in series, what is the resonance frequency?
1. \(600\) radian/sec
2. \(600\) Hz
3. \(500\) radian/sec
4. \(500\) Hz
In an ac circuit, the current is given by \(i=5\sin(100t-\frac{\pi}{2})\) and the ac potential is V = 200 sin(100t) volt. The power consumption is:
1. 20 W
2. 40 W
3. 1000 W
4. 0
1. | \(60\) Hz and \(240\) V |
2. | \(19\) Hz and \(120\) V |
3. | \(19\) Hz and \(170\) V |
4. | \(754\) Hz and \(70\) V |