HSC Physics Module 6 Mixed trial papers

A direct current electric motor has a square armature of 500 turns. Which statement below about this motor is correct?

• The slip rings reverse the current flow in the armature every half turn

• the torque on the armature is a maximum when the plane of the armature is at right angles to the magnetic field

• the torque on the armature is a maximum when the plane of the armature is parallel to the magnetic field

• the back emf causes the net force on the armature to be zero

Which of the following forms of energy is always produced whenever electricity is converted for use in the home or industry?

• heat

• light

• sound

• electromagnetic

A 20 cm length of wire is suspended horizontally from a spring balance. The wire is hanging in a horizontal magnetic field that is perpendicular to the wire. A current flow of 25 A through the wire results in a reading of 0.12 N and when the current is reversed, the reading on the balance is 0.08 N.

What is the magnitude of the magnetic field?

• 4 x 10^-3 T

• 8 x 10^-3 T

• 4 x 10^-1 T

• 8 x 10^-3 T

A transmission line of 5 ohm is to be used to transmit at 1000 W of power

What is the ratio of the energy loss in the line for the current of 1A compared to a current of 10A?

• 1:1

• 1:10

• 1:20

• 1:100

What principle of physics governs the input and output power of a transformer?

• Electromagnetic induction

• The Law of Conservation of Energy

• Lenz's Law

• The motor effect

A current-carrying conductor experiences a force when it is placed in a magnetic field. What is this known as?

• The motor effect

• Electromagnetic induction

• Electromagnetic force

• The right hand palm rule

A conductor of length 40 cm, and carrying 2.5 A is placed at 60^o in a magnetic field directed into the page. The force acting on the conductor is 0.17 N. What is the strength of the magnetic field?

• 0.2 T

• 0.15 T

• 0.015 T

• 0.020 T

The force per unit length between two 50 cm long parallel current-carrying conductors is F Nm^-1. What would the force per unit length between them be if their lengths were increased to 2.0 m?

• 0.025 F

• 0.5 F

• F

• 4 F

The force per unit length between two parallel conductors is 0.2 Nm^-1. The conductors are each 0.4 m long. What is the force between the conductors?

• 0.08 N

• 0.2 N

• 0.5 N

• 1.0 N

Two parallel conductors are 12 cm apart. One carries 3A from left to right, the other carries 4A from right to left. The conductors are each 25 cm long. What is the force between them?

• 5 x 10^-4 N attraction

• 5 x 10^-4 N repulsion

• 5 x 10^-6 N attraction

• 5 x 10^-6 N repulsion