A metallic weight is suspended from a metal spring If now a

A metallic weight is suspended from a metal spring. If now a current it passed through the spring, the spring will contract, raising the weight. the weight will not move. whether or not the weight moves up or down depends on what the weight is made of (i.e whether or not it a magnetizable). the spring will extend, lowering the weight None of these are true. A 5 H inductor carries a current of 2 amps. How can a self-induced EMF of 50 volts be made to appear across the inductor? Change the current at the rate of 10 amps/sec. Change the current uniformly to zero in 20 seconds. Change the current to 10 amps. Break the circuit instantaneously. None of these. What is the essential difference between microwaves and blue light? One is a form of radiation, the other is not. One has an electric charge, the other does not. There is no essential difference in the nature of microwaves and blue light other than a difference in frequency and wavelength. One undergoes refraction, the other does not, Blue light is a beam of photons, Microwaves are not photons. As shown in the figure, a coil of wire is placed in the xy-plane, central on the z-axis. A solenoid is centered on the 2-axis and is carrying a steady dc current. Which one of the following actions will not result induce an emf in the coil? Rotate the owl about the z-axis. Change the current in the solenoid. Move the coil toward point P. Rotate the coil about they-axis. Rotate the coil about the x-axis.

Solution

Since each loop of a spring will have currents in the same direction, each loop will attract the adjacent loops and therefore the spring will be compressed. Answer- A. V = -L*di/dt. So, the answer will be A as rate of change of current induces the voltage. Answer- C. Answer- A. Since, z is the axis of solenoid, rotation about it will not induce an emf in the coil.