Faradays Laws of EMI - UNSOLVED PRACTICE SET

Q7. State Faraday's two laws of electromagnetic induction in your own words.

Q8. A coil of 100 turns experiences a change in flux from 0.02 Wb to 0.08 Wb in 0.5 seconds. Calculate the induced EMF.

Q9. Why is electromagnetic induction called a "non-conservative" phenomenon? Explain briefly.

Q10. A student moves a magnet towards a coil and observes a deflection in the galvanometer. What happens to the deflection if the magnet is moved away? Explain using Faraday's laws.

Q11. A circular loop of wire is placed in a uniform magnetic field. Under what conditions will an EMF be induced in the loop?

Q12. The magnetic flux through a coil changes from 5 mWb to 15 mWb in 0.2 s. The coil has 50 turns. Calculate the average induced EMF.

Q13. State and explain Faraday's laws of electromagnetic induction with a suitable diagram. Explain how these laws form the basis of electric power generation.

Q14. A rectangular loop of dimensions 10 cm × 20 cm has 200 turns. It is placed in a uniform magnetic field of 0.4 T perpendicular to the plane of the loop. The field is reduced to zero in 0.5 seconds.

(a) Calculate the initial magnetic flux through the loop.

(b) Calculate the induced EMF.

(c) If the loop resistance is 5 Ω, calculate the induced current.

(d) Calculate the total charge that flows through the loop during this process.

Q15. Explain the experimental setup Faraday used to discover electromagnetic induction. Describe what happens when (a) a magnet is pushed into a coil, (b) a magnet is withdrawn, and (c) the magnet is held stationary inside the coil.

Q16. In a school physics lab, a student performs Faraday's experiment using a solenoid with 500 turns and cross-sectional area 20 cm². A bar magnet is pushed into the solenoid, increasing the magnetic field from 0 to 0.3 T in 0.4 seconds.

(a) Calculate the change in magnetic flux through the solenoid.

(b) Calculate the induced EMF.

(c) If the solenoid is connected to a galvanometer of resistance 20 Ω, calculate the induced current.

(d) The student repeats the experiment with the magnet moving twice as fast. How do the EMF and current change?

(e) If the magnet is held stationary inside the solenoid, what is the EMF? Explain using Faraday's laws.

Q17. A conducting rod of length l = 50 cm rotates with angular velocity ω = 20 rad/s about one end in a uniform magnetic field B = 0.5 T perpendicular to the plane of rotation.

(a) Calculate the area swept by the rod per second.

(b) Using Faraday's law, calculate the induced EMF between the center and the free end.

(c) Derive the expression ε = ½Bωl² and explain why the factor of ½ appears.

(d) If the rod has resistance 2 Ω and the circuit is completed through a stationary ring, calculate the induced current.

(e) A student suggests that the EMF should be Bωl² without the ½. Explain the error in this reasoning using the concept of average velocity.

Q18. A coil of N = 1000 turns and area A = 50 cm² is rotated at 50 revolutions per second in a uniform magnetic field B = 0.2 T. The axis of rotation is perpendicular to the field.

(a) Calculate the maximum magnetic flux through the coil.

(b) Calculate the maximum rate of change of flux and hence the maximum induced EMF.

(c) Write the expression for the instantaneous EMF as a function of time.

(d) Calculate the average EMF over one complete revolution.

(e) Explain why this principle is used in AC generators and calculate the frequency of the generated AC.