5.4 Magnetic Effects of Electric Currents

A current of 3.0 mA flows in a wire of length 2.0 m. It is placed in a magnetic field of flux density 4 T such that the angle between the current and the field is 90^­º.

What is the magnitude of the magnetic force on the wire?

A proton, p, moves normally across a magnetic field of flux density B T with a speed of v m s^–1.

What is the magnitude of force exerted on the particle?

A negatively charged particle is at rest in a magnetic field B. The force on the particle is:

An electron enters a region of a magnetic field.

In which case is the initial force on the electron directed towards the bottom of the page?

Two long parallel wires carry equal currents in opposite directions. What field do the two wires produce at point Y, which is midway between the wires and on the plane of the paper?

A beam of electrons enters a region in which there are uniform magnetic and electric fields directed at right angles to each other. The field strengths are adjusted such that the beam remains undeflected, as shown in the diagram below.

Which of the following statements is incorrect?

A plotting compass is placed next to a vertical wire AB. When there is no current in the wire, the compass points North due to an external magnetic field.

Which diagram shows a possible direction for the compass to point when a current passes from A to B?

An alpha particle travelling at speed v perpendicular to a magnetic field of strength B experiences a force F.

What is the force acting on an electron travelling at  perpendicular to a magnetic field of strength ?

A proton p is at downwards from top to bottom between the poles of two horizontal magnets.

The magnetic force on the proton is: