Magnetic Effects of Electric Current Practice
Solve chapter-level practice questions for Magnetic Effects of Electric Current with reveal-only solutions and quick revision support.
Practice Set 1 — Magnetic Field and Field Lines
Properties of magnetic field lines and Oersted's experiment.
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Practice Set 2 — Electromagnet and Its Uses
Solenoid, electromagnet construction, and applications.
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Practice Set 3 — Force on Conductor and Fleming's Left-Hand Rule
Motor principle, direction of force, and left-hand rule applications.
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Practice Set 4 — Electric Motor
Construction, working, role of commutator, and uses.
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Practice Set 5 — Electromagnetic Induction and AC Generator
Faraday's experiments, induced current, and generator working.
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Practice Set 6 — Domestic Circuits and Safety
Live/neutral/earth wires, fuse, MCB, earthing, and overloading.
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Quick Q&A Before You Revise
What is the easiest way to differentiate a motor and a generator?
A motor converts electrical energy into mechanical energy (electricity in → rotation out) and uses Fleming's left-hand rule. A generator converts mechanical energy into electrical energy (rotation in → electricity out) and uses Fleming's right-hand rule. Motor has a split-ring commutator; AC generator has slip rings.
Why is the commutator called a split-ring commutator?
The commutator consists of two insulated half-rings connected to the two ends of the rotating coil. As the coil turns, each brush contacts the opposite half-ring after every half rotation. In a DC motor this reverses the current in the coil, keeping the turning effect in the same rotational direction. It is called a split-ring commutator because the conducting ring is divided into two insulated halves.
Why does a galvanometer show no deflection when a magnet is held stationary inside a coil?
Electromagnetic induction occurs only when there is a change in magnetic flux. When the magnet is stationary inside the coil, the flux is constant (not changing), so no EMF is induced and no current flows. The galvanometer shows zero deflection. Moving the magnet — whether in or out — changes the flux and induces a current.
Can alternating current be used to run a DC motor?
A standard permanent-magnet DC motor is designed for direct current. On India's 50 Hz AC supply, current completes 50 cycles and reverses direction 100 times each second, so the torque would also reverse instead of producing smooth one-way rotation. Universal motors, such as those used in many mixers and grinders, are specially designed so that field and armature currents reverse together and can operate on either AC or DC.
Why is it more dangerous to touch the live wire than the neutral wire?
The live wire is at 230 V potential (high potential). If a person standing on the ground touches the live wire, current flows from the live wire, through the person's body, to the earth (ground, which is at zero potential). This gives a serious electric shock. The neutral wire is at zero potential (same as earth), so touching it alone does not normally cause a shock — there is no potential difference between the neutral wire and the earth.
If the magnetic flux through a coil increases, what happens to the induced current?
According to Lenz's law, the induced current will flow in a direction such that it opposes the increase in flux. So the induced current creates its own magnetic field that opposes the original increasing flux. Lenz's law is a consequence of conservation of energy — if the induced current aided the increase in flux, it would perpetually amplify itself without any energy input, which is impossible.