In A Dynamo, A Coil Of Area 0.2 M2 and Having 100 Turns Rotates In A Magnetic Field of 0.1 Wb m–2 with An Angular Velocity Of 100 rad s–1. The Output Terminals Are Connected Through A Resistance of . Calculate The torque , As A Function Of Time t, Required To Keep The Coil Rotating.

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In a dynamo, a coil of area 0.2 m2 and having 100 turns rotates in a magnetic field of 0.1 Wb m–2 with an angular velocity of 100 rad s–1. The output terminals are connected through a resistance of . Calculate the torque , as a function of time t, required to keep the coil rotating.


Correct option is

4 sin 100t

In usual notations, the maximum value of the emf induced in the coil is given by  



The maximum current in the circuit is 


The instantaneous current in given by 


Let l be the length and b the breadth of the coil (assumed to be rectangular), carrying current i in magnetic field B. The forces experienced by each longer arm, N i B l, from a couple of moment . The torque experienced by the rotating coil is thus given by 




An opposite torque of magnitude 4 sin 100t newton-meter is required is keep the coil rotating with uniform angular speed.



A (100w, 200v) bulb is connected to a 160v supply. The power consumption would be


The induced emf in armature will be zero, when armature is rotated at an angle


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Resonance  frequency of a circuit is f if the capacitance is made 4 times the initial value , then the resonance frequency will become


In and A.C. circuit , minimum voltage of 423 Volt. Its effective voltage is


The  average power  dissipation in a pure capacitor in A.C. circuit is


A 100-turn rectangular coil of size 0.20 m × 0.10 m rotates in a magnetic field of 0.003 Wb m–2 with a frequency of 1200 rpm about an axis normal to the field. Find the maximum value of the induced emf


An a.c. generator consisting of a coil of 100 turns and cross-sectional area of 3 m2 is rotating at a constant angular speed of 60 rad s–1 in a uniform magnetic field of 0.04 T. The resistance of the coil is 500 . Calculate maximum current drawn from the generator, and power dissipation in the coil. From where does the power come? 


An a.c. generator consists of a coil of 50 turns and area 2.5 m2 rotating at an angular speed of 60 rad s–1 in a uniform magnetic field of 0.30 T. The resistance of the circuit including that of the coil is 500 . Find the maximum current drawn from the generator.    


The electric main in a house is marked 220V-50Hz. Write down the equation for instantaneous voltage.