HSC Science (Electronics) 12th Standard Board Exam - Maharashtra State Board Question Bank Solutions for Physics

State Wein's displacement law

Obtain an expression for average power dissipated in a purely resistive A.C. circult. 

Find the ratio of the potential differences that must be applied across the parallel and series combination of two capacitors C₁ and C₂ with their capacitances in the ratio 1 : 2 so that the energy stored in the two cases becomes the same.

Choose the correct option:

A standing wave is produced on a string clamped at one end and free at the other. The length of the string ______.

A resistor of 500 Ω and an inductance of 0.5 H are in series with an AC source which is given by V = `100 sqrt2` sin (1000 t). The power factor of the combination is ______.

In a series LCR circuit, the phase difference between the voltage and the current is 45°. Then the power factor will be ______.

What is wattles current?

When an AC source is connected to an ideal inductor show that the average power supplied by the source over a complete cycle is zero.

Prove that an ideal capacitor in an AC circuit does not dissipate power

(a) An emf e = e₀ sin ωt applied to a series L - C - R circuit derives a current I = I₀sinωt in the circuit. Deduce the expression for the average power dissipated in the circuit.
(b) For circuits used for transporting electric power, a low power factor implies large power loss in transmission. Explain.

An AC source generating a voltage e = e₀sinωt is connected to a capacitor of capacitance C. Find the expression for the current i flowing through it. Plot a graph of e and i versus ωt.

A light bulb is rated 100W for 220 V AC supply of 50 Hz. Calculate

1. resistance of the bulb.
2. the rms current through the bulb

An AC circuit consists of only an inductor of inductance 2 H. If the current is represented by a sine wave of amplitude 0.25 A and frequency 60 Hz, calculate the effective potential difference across the inductor. (π = 3.142)

Alternating emf of e = 220 sin 100 πt is applied to a circuit containing an inductance of (1/π) henry. Write an equation for instantaneous current through the circuit. What will be the reading of the AC galvanometer connected in the circuit?

A 25 μF capacitor, a 0.10 H inductor, and a 25Ω resistor are connected in series with an AC source whose emf is given by e = 310 sin 314 t (volt). What is the frequency, reactance, impedance, current, and phase angle of the circuit?

A 100 μF capacitor is charged with a 50 V source supply. Then source supply is removed and the capacitor is connected across an inductance, as a result of which 5A current flows through the inductance. Calculate the value of the inductance.

Prove that under certain conditions a magnet vibrating in a uniform magnetic field performs angular S.H.M.

A wave of frequency 500 Hz is traveling with a speed of 350 m/s. (a) What is the phase difference between two displacements at a certain point at times 1.0 ms apart? (b) what will be the smallest distance between two points which are 45° out of phase at an instant of time?

Two sources of sound are separated by a distance of 4 m. They both emit sound with the same amplitude and frequency (330 Hz), but they are 180° out of phase. At what points between the two sources, will the sound intensity be maximum?

A toroidal ring made from a bar, of length 1 m and diameter 1 cm, bent into a circle. It is wound tightly with 100 turns per centimeter. If the permeability of the bar is equal to that of free space, calculate
(a) the magnetic field inside the bar when the current through the turns is 100 A
(b) the self-inductance of the coil.