Exam MC

What substance would not be attracted by a magnet?

Copper

Describe magnetic field lines.

Show the strength and direction of magnetic field, become widely spread as the force weakens.

What will happen when a magnet is heated?

It will become weaker.

Describe a magnetic domain.

A group of atoms with their magnetic axes lined up in the same direction.

What is it called when something is temporarily magnetized?

Induction.

The strength of a magnetic feild of a coil can be increased by what?

• Increasing the current

• Increasing the number of loops

• Wrapping it around an iron core

What would cause the armature of a DC motor to turn faster?

• increasing the current

• Increasing the turns

• Increasing the strength of the magnetic feild

If a split-ring communicator of a DC motor was replaced with a solid commutator ring, what would happen the the armature?

It would stop when the coil was parallel to the magnetic feild.

A conductor would be attracted to a magnet when…

The conductor caintains moving electrons.

What did Heinrich Lenz state?

The direction of an induced current produces a magnetic field that opposes the inducing field.

What does not affect the size of a induced current in a coil?

Direction of the windings in the coil.

When a permanent magnet is held ready in the Center of a coil, the galvanometer will indicate…

No current.

What factor increase the output of a generator?

• increasing the rate of rotation

• Increasing the strength of the magnets

• Increasing the number of coils

If the connections to a step-up transformer are reversed and the secondary coil is now the primary coil, what will happen?

The transformer will step down the potential difference.

What does a step-down transformer change?

High potential difference to low potential difference.

What is the advantage of AC power over DC power?

AC power allows the operation of transformers.

What does the speed of any mechanical wave as it propagates through a medium depend on?

The type of medium that it travels through.

What is the shortest time interval in which a wave motion completely repeats itself?

A period.

Which way do the particles move in a transverse wave?

Particles move forward with the wave.

How is energy propagated in longitudinal waves?

It is propagated by crests and troughs.

How do waves bend as they travel through small opening or past corners?

Diffraction.

What is produced during complete destructive interference?

A node

What property affects intensity or loudness?

Amplitude.

What does the speed of sound that goes through air depend on?

Tempurature.

During destructive interference what is produced?

A quieter sound.

What causes waves to echo?

Reflection.

Sound waves are…

Longitudinal.

What does pitch depend on?

Loudness.

What does Mach number represent?

The ratio of an objects speed to the speed of sound in air at that location.