If the RMS current in a \(50~\text{Hz}\) AC circuit is \(5~\text{A}\), the value of the current \(\frac{1}{300}~\text{s}\) after its value becomes zero is:
1. \(5\sqrt2~A\)
2. \(5\sqrt{\frac32}~A\)
3. \(\sqrt{\frac56}~A\)
4. \(\frac{5}{\sqrt2}~A\)
An alternating current generator has an internal resistance and an internal reactance . It is used to supply power to a passive load consisting of a resistance and a reactance . For maximum power to be delivered from the generator to the load, the value of is equal to :
1. zero
2. Xg
3. -Xg
4. Rg
When a voltage measuring device is connected to AC mains, the meter shows the steady input voltage of \(220~\text{V}\). This means:
1. | input voltage cannot be AC voltage, but a DC voltage |
2. | maximum input voltage is \(220~\text{V}\) |
3. | the meter reads not v but \(<v^2>\) and is calibrated to read \(\sqrt{<v^2>}\) |
4. | the pointer of the meter is stuck by some mechanical defect |
Which of the following combinations should be selected for better tuning of an LCR circuit used for communication?
1. R = 20 Ω , L = 15 H , C = 35 μF
2. R = 25 Ω , L = 2 . 5 H , C = 45 μF
3. R = 15 Ω , L = 3 . 5 H , C = 30 μF
4. R = 25 Ω , L = 1 . 5 H , C = 45 μF
An inductor of reactance \(1~\Omega\) and a resistor of \(2~\Omega\) are connected in series to the terminals of a \(6~\text{V}\) (RMS) AC source. The power dissipated in the circuit is:
1. \(8~\text{W}\)
2. \(12~\text{W}\)
3. \(14.4~\text{W}\)
4. \(18~\text{W}\)
The output of a step-down transformer is measured to be 24 V when connected to a 12 W light bulb. The value of the peak current is:
1. 1/ A
2. A
3. 2 A
4. 2A
As the frequency of an AC circuit increases, the current first increases and then decreases. What combination of circuit elements is most likely to comprise the circuit?
(a) Inductor and capacitor
(b) Resistor and inductor
(c) Resistor and capacitor
(d) Resistor, inductor, and capacitor
Choose the correct option.
1. (b, c)
2. (c, d)
3. (b, d)
4. (a, d)
In an alternating current circuit consisting of elements in series, the current increases on increasing the frequency of the supply. Which of the following elements are likely to constitute the circuit?
(a) Only resistor
(b) Resistor and an inductor
(c) Resistor and a capacitor
(d) Only a capacitor
Choose the correct option.
1. (b, c)
2. (a, d)
3. (b, d)
4. (c, d)
Electrical energy is transmitted over large distances at high alternating voltages. Which of the following statements is (are) correct?
a. | For a given power level, there is a lower current. |
b. | Lower current implies less power loss. |
c. | Transmission lines can be made thinner. |
d. | It is easy to reduce the voltage at the receiving end using step-down transformers. |
1. (a, b, c)
2. (a, b, d)
3. (b, c, d)
4. (c, d)
For an L-C-R circuit, the power transferred from the driving source to the driven oscillator is .
a. | Here, the power factor cosϕ ≥ 0 , P ≥ 0 . |
b. | The driving force can give no energy to the oscillator (P = 0) in some cases. |
c. | The driving force cannot syphon out (P<0) the energy out of the oscillator. |
d. | The driving force can take away energy out of the oscillator. |
1. (a, b, c)
2. (a, c, d)
3. (b, c, d)
4. (c, d)