NCERT Solutions for Class 12 Help.html Physics Part I Chapter 6 Electromagnetic Induction

State the principle of an ac generators and explain its working with the help of a labelled diagram. Obtain the expression for the emf induced in a coil havin N turns each of cross-sectional area, rotating with a constant angular speed 'ω' in a magnetic field $\overrightarrow{\mathrm{B}}$, directed perpendicular to the axis of rotation.

An aeroplane is flying horizontally from west to east with a velocity of 900 km/hour. Calculate the potential difference developed between the ends of its wings having a span of 20 m. The horizontal component of the Earth’s magnetic field is 5 × 10^–4 T and the angle of dip is 30°.

An inductor of inductance L = 400 mH and resistors of resistances R1 = 2 Ω and R2 = 2 Ω is connected to a battery of emf 12 V as shown in the figure. The internal resistance of the battery is negligible. The switch S is closed at t = 0. The potential drop across L as a function of time is 

• 6^e–5t V

• 
• 

• 12^e–5t V

Two identical conducting wires AOB and COD are placed at right angles to each other. The wire AOB carries an electric current I₁ and COD carries a current I₂. The magnetic field on a point lying at a distance ‘d’ from O, in a direction perpendicular to the plane of the wires AOB and COD, will be given by

The flux linked with a coil at any instant ‘t’ is given by
φ= 10t²- 50t +250
The induced emf at t = 3 s is

• 190 V

• −190 V

• -10 V

• 10 V

Two concentric coils each of radius equal to 2π cm are placed at right angles to each other. 3 Ampere and 4 ampere are the currents flowing in each coil respectively. The magnetic induction in Weber/m² at the centre of the coils will be (µ0 = 4π × 10⁻⁷ Wb/A^-m)

• 12 × 10⁻⁵

• 10⁻⁵

• 5 × 10⁻⁵

• 7 × 10⁻⁵

A coil of inductance 300 mH and resistance 2Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in

• 0.05 s

• 0.1 s

• 0.15 s

• 0.3 s

The self inductance of the motor of an electric fan is 10 H. In order to impart maximum power at 50 Hz, it should be connected to a capacitance of

• 4µF

• 8µF

• 1µF

• 2µF

A coil having n turns and resistance 4R Ω. This combination is moved in time t seconds from a magnetic field W₁ weber to W₂ weber. The induced current in the circuit is

A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radians per second. If the horizontal component of earth’s magnetic field is 0.3 × 10⁻⁴ T, then the e.m.f. developed between the two ends of the conductor is

• depends on the nature of the metal used

• depends on the intensity of the radiation

• depends both on the intensity of the radiation and the metal used

• is the same for all metals and independent of the intensity of the radiation.