Physics Grade 12 Sheet

A circular coil with an area of 5.0 × 10² m² and with 500 turns of wire is placed in a uniform magnetic field perpendicular to the plane of the coil. If the field changes in value from -0.100 T to +0.150 T in an interval of 0.500 s, what is the induced emf in the coil?

• -12.5 V

• 125 V

• 188 V

• 252 V

A coil with a wire that is wound around a 2.0 m² hollow tube 35 times. A uniform magnetic field is applied perpendicular to the plane of the coil. If the field changes uniformly from 0.00 T to 0.55 T in 0.85 s, what is the induced emf in the coil?

• –33 V

• 33 V

• –45 V

• 45 V

A coil with a wire that is wrapped 40.0 turns around a 0.5 m² hollow tube. A uniform magnetic field is applied perpendicular to the plane of the coil. The field changes uniformly from 0.00 T to 0.95 T in 2.0 s. If the resistance in the coil is 3.0 Ω, what is the magnitude of the induced current in the coil?

• 11 A

• –11 A

• 9.5 A

• –9.5 A

A step-up transformer used on a 120 V line has 95 turns on the primary and 2850 turns on the secondary. What is the potential difference across the secondary?

• 30 V

• 1800 V

• 2400 V

• 3600 V

A step-down transformer has 2500 turns on its primary and 5.0 ×10¹ turns on its secondary. If the potential difference across the primary is 4850 V, what is the potential difference across the secondary?

• 1.0 V

• 110 V

• 97 V

• 240 V

By what factor is the self-induction of a coil changed if its number of coil turns is tripled?

• ⅓

• 3

• 6

• 9

Which conversion process is the basic function of the electric motor?

• mechanical energy to electrical energy

• electrical energy to mechanical energy

• low voltage to high voltage, or vice versa

• alternating current to direct current

Which conversion process is the basic function of the electric generator?

• mechanical energy to electrical energy

• electrical energy to mechanical energy

• low voltage to high voltage, or vice versa

• alternating current to direct current

A loop of wire is held in a vertical position at the equator with the face of the loop facing in the east-west direction. What change will induce the greatest current in the loop?

• raising the loop to a higher elevation

• moving the loop north

• rotating the loop so its face is vertical

• rotating the loop so its face is north-south

According to Lenz's law, the magnetic field of an induced current in a conductor will

• enhance the applied field.

• heat the conductor.

• increase the potential difference.

• oppose a change in the applied magnetic field.