Exploring DC Motors and Electromagnetism (21 Pre-Quiz)

What is the principle behind electromagnetic induction?

• The generation of electric current by a stationary magnetic field

• The generation of electric current by a changing magnetic field

• The generation of magnetic fields by electric currents

• The generation of electric current by a constant electric field

Which component of a DC motor is responsible for reversing the direction of current?

• Armature

• Commutator

• Brushes

• Field Magnet

What is the role of brushes in a DC motor?

• To provide a magnetic field

• To supply current to the armature

• To reverse the direction of current

• To increase motor speed

Calculate the efficiency of a DC motor if the input power is 100 W and the output power is 80 W.

• 60%

• 70%

• 80%

• 90%

Which of the following is an application of electromagnetism?

• Solar panels

• Wind turbines

• Electric generators

• Geothermal plants

Explain how a magnetic field can exert a force on a current-carrying conductor.

• The magnetic field creates a voltage in the conductor

• The magnetic field aligns the electrons in the conductor

• The magnetic field interacts with the moving charges in the conductor

• The magnetic field increases the resistance of the conductor

Which of the following best describes the function of the armature in a DC motor?

• It generates a magnetic field

• It converts electrical energy into mechanical energy

• It supplies current to the motor

• It reverses the direction of current

Describe the relationship between the speed of a DC motor and the applied voltage.

• The speed is directly proportional to the square of the voltage

• The speed is inversely proportional to the voltage

• The speed is directly proportional to the voltage

• The speed is independent of the voltage

A DC motor has an input power of 150 W and an output power of 120 W. What is the motor's efficiency?

• 70%

• 80%

• 85%

• 90%

What happens to the magnetic field around a wire when the current through it is increased?

• The magnetic field decreases

• The magnetic field remains the same

• The magnetic field increases

• The magnetic field disappears