Motion in Electromagnetic Fields (HL IB Physics)

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?

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:

A small point charge +q descends vertically into a region where there is an electric field. The equipotentials of this field are shown. 

What is the subsequent path followed by the particle?  

A charged particle in an electric field will experience a force on it that will cause it to move. The three particles X, Y and Z are experiencing a force which deflects their motion as shown. What three particles could X, Y and Z be?

A straight wire PQ carrying a constant current I is placed perpendicularly to a uniform magnetic field, as represented by the dotted line in the diagram below.

The current-carrying wire is then rotated anti-clockwise through an angle θ about an axis perpendicular to the plane of the diagram.

Which of the following graphs shows how the magnitude of the magnetic force F on the wire varies with θ in the rangeradians?

A current I = 200 mA is passed through a pivoted square wire frame, of side length 50 cm, which is initially balanced.

A bar magnet is placed near one of the edges of the frame, which causes it to tilt. A rider of mass m = 10 g and length 10 cm is then placed at the midpoint of the opposite edge on the wire frame, such that the frame regains its balance, as shown in the diagram below.

What is the magnitude of the magnetic flux density near the magnet?

Three long parallel straight wires, X, Y and Z, are equally separated and placed in the same plane in a vacuum. They carry a current of I, 2I and 4I respectively, as shown: 

It is known that the magnetic flux density B at a distance r due to a long straight wire carrying current I is given by: 

where μ₀ is the permeability of free space.

What is the force per unit length acting on wire X? 

A liquid that contains a suspension of positive and negative ions flows through a square pipe as shown. 

An electric field is set up in the pipe

A direct current I is made to pass through a swing that is mounted to the ceiling, such that it can swing freely. A permanent magnet is fixed directly below, with its south pole S facing the swing. 

The swing will

Two long parallel wires carry equal currents in opposite directions. What exists at the point in space that is exactly midway between the wires and in the plane of the wires? 

A loosely-coiled light spring is suspended from a fixed point. 

When the switch is closed, 

A doubly charged ion moves in a uniform magnetic field of flux density B in a circle of orbital radius r at speed v. What is the flux density which would maintain an ion of charge 4e of the same mass in a circle of the same orbital radius at the same speed? 

An electron moves along the axis of a solenoid carrying a current. 

Which of the following statements is correct about the magnetic force on the electron? 

A particle P with charge q and mass m is fired with kinetic energy K into a region between two metal plates.

If the magnetic flux density between the plates is B, what is the minimum magnitude of B which ensures the particle does not collide with the opposite plate?