Ch3 - L3 Electric Generator

A dynamo coil rotates 4200 rotations/minute in a magnetic field of flux density 0.05T. If the number of turns of the coil is 100 turns and the area of each of them is 25cm². The maximum emf equals ……….. and the effective emf equals ……….

• 5.5V, 3.9V

• 5.5V, 330V

• 330V, 3.9V

• 330V, 5.5V

The following graph shows the relation between the current intensity (I) produced from a simple dynamo its coil resistance is 10Ω with the time of its coil rotation (t). The angular velocity equals ….…. and the effective generated emf equals ……….

• 78.5rad/sec, 14.14V

• 157rad/sec, 14.14V

• 78.5rad/sec, 1.414 V

• 157rad/sec, 1.414V

The ratio between the average induced emf during half cycle to the effective emf is

• Equal to one

• More than one.

• Less than one.

• No correct answer.

The graph represents the electromotive force (emf) generated in the dynamo coil, time for revolving, starting from normal position till (emf) becomes -50V for the first time equals

• 50 sec

• 29.16 sec

• 10.5 sec

• 4.167 sec

A rectangular coil of 100 turns has dimensions of 10 cm by 15 cm. The axis of rotation is perpendicular to the direction of the magnetic field of strength 0.7 T, and it is rotating at 600 rpm (rotation per minute).. The effective emf induced in the coil equals ……. and the time of reaching half the maximum value of emf is ……..

• 66V, 0.0166sec

• 46.662V, 8.33×10-3sec

• 93.662V, 8.33×10-3sec

• 66V, 120sec

• 240 V

• 169.7 V

• 120 V

• 45 V

The rotation part is in contact with the graphite brushes in alternating current dynamo is ……….. and the rotation part is in contact with the graphite brushes in uni-directional current dynamo is …………

• commutator, two slip rings

• commutator, commutator

• two slip rings, two slip rings

• two slip rings, commutator

The graph represent the emf generated in the dynamo coil during half cycle, the average emf through half cycle of the coil

• 14 V

• 22 V

• 11 V

• 15.5 V

An AC dynamo is produced a maximum emf of 100 Volt, so The average electromotive force through the (1/4) revolution of its coil

• 10.9 V

• 44.6 V

• 50 V

• 63 V

A 2cm by 1.5cm rectangular coil has 300 turns and rotates in a region that has a magnetic field of 0.7T, the coil connected with a resistor of 3Ω. When the coil rotates at 60Hz. The value of maximum emf is …… and the consumed energy in the resistor during one cycle of AC current equals ……….

• 23.76V, 3.1J

• 23.76V, 1.6J

• 16.79V, 1.6J

• 16.79V, 3.1J