Q. No.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)
When an AC voltage of 220 V is applied to the capacitor C
| a. | the maximum voltage between plates is 220 V. |
| b. | the current is in phase with the applied voltage. |
| c. | the charge on the plates is in phase with the applied voltage. |
| d. | power delivered to the capacitor is zero. |
Choose the correct option
1. (b, c)
2. (a, d)
3. (b, d)
4. (c, d)
The line that draws power supply to your house from the street has
(a) zero average current
(b) 220 V average voltage
(c) voltage and current out of phase by
(d) voltage and current possibly differing in phase
1. (b, c)
2. (a, d)
3. (b, d)
4. (a, c)
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. \(18~\text{W}\)
To reduce the resonant frequency in an LCR series circuit with a generator:
| 1. | the generator frequency should be reduced |
| 2. | another capacitor should be added in parallel to the first |
| 3. | the iron core of the inductor should be removed |
| 4. | the dielectric in the capacitor should be removed |
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 |
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