What magnetic field is produced around a straight wire carrying an electric current?

Straight magnetic field lines parallel to the wire in the direction of current Circular magnetic field lines centred on the wire, whose direction is given by the right-hand rule Radial magnetic field lines pointing away from the wire in all directions No magnetic field, because moving charges cancel the electric field

A solenoid has 200 turns and carries a current of 3 A. How could an engineer double the magnetic field strength inside the solenoid without changing the current?

Halve the length of the solenoid while keeping 200 turns Double the number of turns to 400 Reverse the direction of current flow Use a thicker wire with the same number of turns

Why is a soft iron core placed inside a solenoid to make an electromagnet?

Iron is a good conductor of electricity, reducing resistance in the coil Iron has high magnetic permeability, concentrating the magnetic flux and greatly increasing field strength Iron prevents heat from escaping the solenoid, maintaining temperature Iron acts as an insulator to prevent current leaking from the coil

What key advantage does an electromagnet have over a permanent magnet in an industrial crane used to lift scrap metal?

Permanent magnets are too weak for industrial use, while electromagnets are always stronger The electromagnet can be switched on and off, allowing the crane to pick up and release metal on demand Electromagnets work at any temperature, while permanent magnets lose their magnetism above 20 °C Electromagnets have no magnetic field when not carrying current, reducing safety risks during maintenance only

What is electromagnetic induction?

The flow of current through a conductor placed in a steady magnetic field The generation of an EMF in a conductor due to a changing magnetic flux through it The force on a current-carrying conductor in an external magnetic field The production of a magnetic field around a current-carrying wire

A coil of 50 turns experiences a change in magnetic flux of 0.04 Wb in 0.2 seconds. What is the magnitude of the induced EMF?

0.4 V 2 V 10 V 50 V

What does Lenz's law tell us about the direction of an induced current?

The induced current always flows in the same direction as the original current in the nearby conductor The induced current flows in a direction that opposes the change in magnetic flux that caused it The induced current flows perpendicular to the magnetic field at all times The induced current always flows clockwise when viewed from the north pole of the inducing magnet

A transformer has 400 turns on the primary coil and 100 turns on the secondary coil. If the primary voltage is 240 V, what is the secondary voltage?

240 V 120 V 60 V 960 V

An ideal step-up transformer increases voltage from 230 V to 11,000 V. If the primary current is 50 A, what is the secondary current?

50 A Approximately 1.05 A 2,391 A 0.021 A

Why must transformers use alternating current (AC) rather than direct current (DC)?

DC has too high a voltage for transformer cores to handle safely AC produces a continuously changing magnetic flux in the core, which is needed to induce an EMF in the secondary coil DC reverses direction too rapidly for the transformer turns ratio to function correctly AC is always at lower voltage than DC and is therefore safer for coil windings

How does an AC generator (alternator) produce electricity?

Two fixed magnets push charge through a stationary coil using electrostatic force A coil rotates in a magnetic field, continuously changing the flux through it and inducing a sinusoidal AC EMF A DC supply is rapidly reversed by an electronic circuit to simulate AC output Permanent magnets spin to generate heat, which is then converted to electrical energy

What is the Hall effect, and in which real-world sensor is it commonly used?

A longitudinal voltage generated along a wire when current changes direction; used in fuses A transverse voltage generated in a current-carrying conductor in a magnetic field; used in wheel speed sensors and electronic compasses Resistance increase in a conductor placed near a magnet; used in heating elements A resonance phenomenon in AC circuits; used in radio tuners only