Period and Frequency of AC Generator

Q. An electric motor exerts a constant torque $5Nm$ on a flywheel by which it is rotated at the rate of $420rpm$. The power of motor is:

1. $110watt$
2. $150watt$
3. $300watt$
4. $220watt$

Q. If a rotor in a power generator completes 3000 rotations in a minute. What is the frequency of the AC produced if the pair of magnetic poles are used in the generator?

1. 3000 Hz
2. 50 Hz
3. 60 Hz
4. 300 Hz

Q. Maximum voltage produced in an AC generator completing 60 cycles in 30 second is 250 V. What is the period of the armature?

1. 0.5 s
2. 2 s
3. 1 s
4. 30 s

Q. State whether True or False :

1. True
2. False

Q. State two ways to increase the speed of rotation of a $DC$ motor.