Magnetic Effects of Electric Current
Frequently Asked Questions
The region around a magnet or current-carrying conductor within which its magnetic influence can be felt is called a magnetic field.
Imaginary lines that represent the direction and strength of the magnetic field. They emerge from the North pole and enter the South pole.
Outside a magnet: North ? South. Inside the magnet: South ? North, forming closed loops.
A stronger magnetic field.
If we hold the current-carrying conductor with the right hand such that the thumb points in the direction of current, then the curled fingers show the direction of magnetic field lines.
Concentric circles formed around the conductor; strength increases with increase in current and decreases with distance.
\( B \propto \dfrac{I}{r} \), where I is current and r is distance.
The direction of the magnetic field also reverses.
A long coil of closely spaced circular turns of insulated wire.
It produces a uniform strong magnetic field inside it, with a defined North and South pole.
A temporary magnet formed when current passes through a coil wrapped around a soft iron core.
Used in electric bells, cranes, speakers, relays, magnetic locks, etc.
A device that converts electrical energy to mechanical energy.
On the magnetic effect of electric current and force on a current-carrying conductor.
If the thumb, forefinger, and middle finger of the left hand are placed perpendicular: Forefinger = magnetic field, Middle finger = current, Thumb = direction of force.
The phenomenon in which an electric current is induced in a conductor when it cuts a changing magnetic field.
Forefinger = magnetic field, Middle finger = induced current, Thumb = motion.
A device that converts mechanical energy to electrical energy using electromagnetic induction.
The wiring and arrangement used to safely distribute electric power in homes.
A safety device that melts and breaks the circuit when excessive current flows.
Inside: nearly parallel and uniformly spaced (strong uniform field). Outside: curved, like bar magnet’s field.
It reverses the direction of current in the coil after every half rotation to maintain continuous rotation.
Because the magnetic field interacts with moving charges, producing mechanical force (Lorentz force).
Electromagnetic induction (generation of current by rotating a coil in a magnetic field).
Electromagnet works only when current flows and can be made stronger; a permanent magnet always retains magnetism.
Electric guitar pickups, power generators, induction cooktops.
They acquire and lose magnetism quickly, making the device efficient.
It indicates how strong the magnetic influence is; measured by the closeness of field lines.
Increase current, increase turns of coil, and use a soft iron core.
To maintain contact between the rotating commutator and external circuit.
Because the field lines are parallel and equally spaced.
A sensitive device that detects small electric currents.
Motor: Electrical ? Mechanical; Generator: Mechanical ? Electrical.
The quantity of magnetic field passing through a given area.
Faster motion of conductor, stronger magnetic field, more coil turns.
To prevent overloading and to allow parallel functioning of gadgets.
Automatically trips when excessive current flows; safer than fuses.
It has a magnetic field with a North and South pole due to molten iron movements in the core.
It is perpendicular to the plane of the loop and increases with current and number of turns.
Motors, generators, transformers, electric bells, speakers, relays, MRI, maglev trains.
The rotating coil in electric motors and generators.
Due to forces acting on opposite sides of the coil in opposite directions.
As electromagnets, inductors, magnetic lenses, and in MRI machines.
Because magnetic monopoles do not exist; magnets always have two poles.
Alternating current (AC) in most household generators.
Used to find direction of force in motors.
Used to determine direction of induced current in generators.
AC is easier to transmit over long distances and can be stepped up/down using transformers.
A current is induced (electromagnetic induction).
“Explain the working of an electric motor with a neat diagram.” (Expected 5-mark answer.)
“Describe the construction and working of an AC generator.”
Fuse, MCB, Earth wire, proper insulation.
It protects users from electric shocks by providing a low-resistance path.
A device that uses electromagnetic induction to generate high voltage from low voltage.
Depends on current, number of turns, and material of core.
When excessive current flows through a circuit due to high power appliances running together.
When live and neutral wires touch each other, causing sudden large current flow.
Magnetic cranes, electric bells, relays, transformers.
The turning effect produced due to forces acting on opposite sides of the coil.
Because it is a good conductor with low resistance.
