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 90º.
What is the magnitude of the magnetic force on the wire?
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 magnetic field at right angles to the plane of the page
An electric field at right angles to the plane of the page
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?
Conventional current flows from right to left in this diagram
The velocity of the electron beam v is equal to the ratio of the magnetic flux density B to the electric field strength E
The magnetic force on the electron beam is in the direction indicated ‘south’
The electric force on the electron beam is in the direction indicated ‘north’
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?