Unit 4 Lesson 2: Electromagnets & Inducing Currents

What causes the magnetism of a permanent magnet?

The motion of electrons in aligned atoms that reinforces the magnetic field of each electromagnet.

How does a magnet pick up paper clips?

The ferromagnetic material in the paper clips realigns under the influence of the magnet’s magnetic field, becoming new magnets.

What can induce a current in a closed circuit without a battery?

A magnetic field.

What is electromagnetic induction?

Formation of a voltage across a conductor in a changing magnetic field.

What energy does a hydroelectric power plant transform to generate electricity?

Kinetic energy.

What is the expected alignment of the magnetic field lines around a current-carrying wire?

Concentric circles around the wire.

How does magnetic resonance imaging (MRI) work?

Hydrogen atoms align with the magnetic field and emit radio waves once the field is shut off.

What happens when a changing magnetic field is placed near a wire?

An electric field generates an electrical current in the wire.

What happens when a magnet is moved back and forth in a coiled wire?

The moving magnet generates a magnetic field that causes an electric current in the wire.

Why are iron shavings gathered at the poles of a horseshoe magnet?

Iron is ferromagnetic; in a magnet's presence, atoms align with the magnetic field, becoming magnets themselves.

What happens to a wire loop in a DC motor when current flows through it?

The loop begins to rotate.

Why does a loop of wire rotate in a DC motor?

The electric current creates a magnetic field that alternates between attraction and repulsion with fixed magnetic poles.

How does the strength of a magnetic field change from 5 cm to 10 cm away from a current-carrying wire?

The strength decreases by a factor of four, inversely proportional to the square of the distance.

Why might Mercury have a magnetic field?

Mercury may have a magnetic field due to its molten iron core, similar to Earth's convection-driven magnetic field.

How would adding extra wire rounds and increasing current affect an electromagnet's strength?

The strength of the magnetic field will increase, proportional to the number of wire rounds and current magnitude.