Science (English Medium) कक्षा १२ - CBSE Important Questions for Physics

A series RL circuit with R = 10 Ω and L = `(100/pi)` mH is connected to an ac source of voltage V = 141 sin (100 πt), where V is in volts and t is in seconds. Calculate

1. the impedance of the circuit
2. phase angle, and
3. the voltage drop across the inductor.

A resistor of 50 Ω, a capacitor of `(25/pi)` µF and an inductor of `(4/pi)` H are connected in series across an ac source whose voltage (in volts) is given by V = 70 sin (100 πt). Calculate:

1. the net reactance of the circuit
2. the impedance of the circuit
3. the effective value of current in the circuit.

Which of the following statements about a series LCR circuit connected to an ac source is correct?

An alternating voltage of 220 V is applied across a device X. A current of 0.22 A flows in the circuit and it lags behind the applied voltage in phase by π/2 radian. When the same voltage is applied across another device Y, the current in the circuit remains the same and it is in phase with the applied voltage.

1. Name the devices X and Y and,
2. Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.

An ideal inductor is connected across an AC source of voltage. The current in the circuit ______.

The primary coil having N_P turns of an ideal transformer is supplied with an alternating voltage V_P. Obtain an expression for the voltage V_S induced in its secondary coil having N_S turns.

Mention two main sources of power loss in real transformers.

What is the ratio of inductive and capacitive reactance in an ac circuit?

The large scale transmission of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped-up because of ______.

Draw the phasor diagram for a series LRC circuit connected to an AC source.

Plot a graph to show the variation of current with a frequency of the ac source, explaining the nature of its variation for two different resistances R₁ and R₂ (R₁ < R₂) at resonance.

When an alternating voltage of 220V is applied across device X, a current of 0.25A flows which lags behind the applied voltage in phase by π/2 radian. If the same voltage is applied across another device Y, the same current flows but now it is in phase with the applied voltage.

1. Name the devices X and Y.
2. Calculate the current flowing in the circuit when the same voltage is applied across the series combination of X and Y.

A series LCR circuit is connected to an ac source. Using the phasor diagram, derive the expression for the impedance of the circuit.

What role dose infra-red radiation play in maintain the Earth’s warmth

What role dose infra-red radiation play in physical therapy?

Identify the part of the electromagnetic spectrum which is:

produced by bombarding a metal target by high speed electrons.

Write the range of frequency of these waves.

If the earth did not have atmosphere, would its average surface temperature be higher or lower than what it is now? Explain.

To which part of electromagnetic spectrum does a wave of frequency 3 × 10¹³ Hz belong?

To which part of the electromagnetic spectrum does a wave of frequency 5 × 10¹⁹ Hz belong?