In an electric motor, which rule gives the direction of the force acting on a current-carrying coil placed in a magnetic field?

Fleming's left-hand rule. Fleming's left-hand rule gives force direction on each current-carrying coil segment. Opposite segment forces can produce a turning effect. The thumb rule gives the wire's field direction. Lenz's law gives the induced response to changing flux. Fleming's right-hand rule concerns motional induction.

A straight wire carries current parallel to a uniform magnetic field. What is its magnetic force?

Zero. The force magnitude is BIL sin θ. Parallel current gives θ = 0°, so sin θ = 0. Maximum force and BIL apply at 90°. BI divided by L is not the force formula.

Which change can induce emf in a stationary coil of fixed area and orientation?

Changing the magnetic field through the coil. A changing magnetic field changes flux through the stationary coil. Faraday's law then gives induced emf. Constant flux does not produce induction around the loop. A stationary unchanged magnet and an identical replacement wire do not supply the required flux change.

What is the split-ring commutator's job in a simple DC motor?

Reverse coil current every half-turn. The split ring reverses coil current every half-turn. That keeps torque in the same rotational sense. Keeping coil current unchanged would reverse the turning tendency after a half-turn. The commutator does not remove the field. Mechanical-to-electrical conversion describes generator operation.

How much time separates successive direction reversals in a sinusoidal 50 Hz current?

10 milliseconds. A 50 Hz cycle lasts 1/50 second, or 20 milliseconds. Direction reverses twice per cycle, so successive reversals are 10 milliseconds apart. Twenty milliseconds is a full cycle. Neither 1 second nor 50 milliseconds matches the half-cycle time.

What output does a simple rotating-coil generator with a split-ring commutator provide?

Unidirectional but pulsating output. The commutator makes the external output unidirectional. Its magnitude still varies, giving pulsating DC rather than constant current. Rotation changes flux, so emf can be produced. A simple slip-ring arrangement instead gives alternating output.

What is protective earth's role for an appliance with an exposed conducting body?

Provide a fault-current path that enables appropriate protection to disconnect the supply. Protective earth provides a fault-current path when a live conductor contacts the body. Appropriate protection can disconnect the supply. Neutral normally provides the operating-current return path. Earthing does not guarantee freedom from every shock, and it does not raise supply voltage.

MCQ QuestionsMy progress

Viewed facing a page, conventional current points out of it through a long straight wire. Which way does its magnetic field turn?

Question 1 of 8

Was this helpful?

Viewed facing a page, conventional current points out of it through a long straight wire. Which way does its magnetic field turn?

Keep practicing

Beyond the answer

Leave a ReplyCancel reply

Discover more from MCQ Questions