CBSE Class 12 Physics Electromagnetic Induction Formulae

NUMERICALS

LEVEL I

1. What is the self-inductance of a coil in which magnetic flux of 40mWb is produced when 2A current flow through it?

2. If the self inductance of an air core inductor increases from 0.01mH. to 100mH on introducing an iron core into it. What is relative permeability of the core used?

3. What is the power dissipated in an a.c circuit in which voltage and current are given by V=230 sin(ωt + /2) and I=10 sinωt ?

4. When a lamp is connected to an a.c. supply it light with the same brightness as when connected to a 12V d.c battery. What is the peak value of alternating voltage?

5. Find the capacitance o frequency 5/Π kHz ?

6. What is the average value of the emf for the shaded part of graph?

7. In a series LCR circuit the voltage across an inductor, a capacitor and a resistor are 20V, 20V and 60V respectively. What is the phase difference between the applied voltage and the current in the circuit?

8. A circular coil of radius 8 cm and 20 turns rotates about its vertical diameter with an angular speed of 50/s in a uniform horizontal magnetic field of magnitude 3 x 10^-2 T. Find the max. and the average value of the emf induced in the coil.

9. The instantaneous current from an a.c. source is I = 5 sin (314 t) ampere. What are the average and rms values of the current?

10. An inductor L, a capacitor 20 F, a resistance Hz. If the current is in phase with voltage, calculate the Inductance L.

LEVEL II

Q1. A conductor of length 1.0 m falls freely under gravity from a height of 10 m so that it cuts the lines of force of the horizontal component of earth’s magnetic field of 3x10-5 Wbm-2. Find the emf induced in the conductor.

Q2. A 0.4 m long straight conductor is moved in a magnetic field of induction 0.9 Wbm-2 with velocity of 7 ms-1. Calculate the maximum emf induced in the conductor.

Q3. A metal disc of radius 200 cm is rotated at a constant angular speed of 60 rads-1 in a plane at right angles to an external field of magnetic induction 0.05 Wbm-2 .Find the emf induced between the centre and a point on the rim.

Q4. Find the maximum value of current when an inductance of one Henry is connected to an a.c. source of 200 volts, 50 Hz.

Q5. What is the inductive reactance of a coil if current through it is 800 mA and the voltage across it is 40 V?

Q6. A transformer has 300 primary turns and 2400 secondary turns .If the primary supply voltage is 230 V, what is the secondary voltage?

Q7. A transformer of 100% efficiency has 500 turns in the primary and 10,000 turns in the secondary coil. If the primary is connected to 220 V supply, what is the voltage across the secondary coil?

Q8. A capacitor in series with a resistance of 30 ohm is connected to a.c. mains. The reactance of the capacitor is 40 ohm. Calculate the phase difference between the current and the supply voltage.

Q9. Determine the impedance of a series LCR-circuit if the reactance of C and L are 250 ohm and 220 ohm respectively and R is 40 ohm.

Q10. A series circuit with L=0.12 H, C=0.48 mF and R=25 ohm is connected to a 220 V variable frequency power supply. At what frequency is the circuit current maximum?

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