EduNinjaDefine the tesla.
Two long straight vertical wires X and Y are separated by a distance of 4.5 cm , as illustrated in Fig. 5.1.
Fig. 5.1
The wires pass through a horizontal card PQRS. The current in wire X is 6.3 A in the upward direction. Initially, there is no current in wire Y .
A current of 9.3 A is now switched on in wire Y . Use your answer in (ii) to calculate the force per unit length on wire Y .
Define the tesla.
Define the tesla.
A horseshoe magnet is placed on a balance. A stiff metal wire is clamped horizontally between the poles, as illustrated in Fig. 5.1.
Fig. 5.1
The magnetic flux density in the space between the poles of the magnet is uniform and is zero outside this region.
The length of the metal wire normal to the magnetic field is 6.4 cm .
When a current in the wire is switched on, the reading on the balance increases by 2.4 g . The current in the wire is 5.6 A .
State and explain the direction of the force on the wire due to the current.
Calculate the magnitude of the magnetic flux density between the poles of the magnet.
flux density =
A stiff straight copper wire XY is held fixed in a uniform magnetic field of flux density , as shown in Fig. 6.1.
Fig. 6.1
The wire X Y has length 4.7 cm and makes an angle of with the magnetic field.
Calculate the force on the wire due to a constant current of 5.4 A in the wire.
force = N
A uniform magnetic field has constant flux density B. A straight wire of fixed length carries a current I at an angle to the magnetic field, as shown in Fig. 6.1.
Fig. 6.1
The current I in the wire is changed, keeping the angle constant.
On Fig. 6.2, sketch a graph to show the variation with current I of the force F on the wire.
Fig. 6.2
The angle between the wire and the magnetic field is now varied. The current I is kept constant. On Fig. 6.3, sketch a graph to show the variation with angle of the force F on the wire.
Fig. 6.3
Two long straight parallel copper wires A and B are clamped vertically. The wires pass through holes in a horizontal sheet of card PQRS, as shown in Fig. 7.1.
Fig. 7.1
A direct current is now passed through wire B in the same direction as that in wire A. The current in wire B is larger than the current in wire A.
On Fig. 7.1, draw an arrow in the plane PQRS to show the direction of the force on wire B due to the magnetic field produced by the current in wire A.
Wire A also experiences a force. State and explain which wire, if any, will experience the larger force.
Define magnetic flux density.
Electrons are moving in a vacuum with speed . The electrons enter a uniform magnetic field of flux density 4.8 mT . Fig. 6.1 shows the path of the electrons.
Fig. 6.1
The path of the electrons remains in the plane of the page.
State the direction of the magnetic field.
Define the tesla.
State the two conditions that must be satisfied for a copper wire, placed in a magnetic field, to experience a magnetic force.
1
2
Define magnetic flux density.
An insulated rectangular coil of wire, consisting of 40 turns, is suspended in a cradle from a newton meter, as shown in Fig. 7.1.
Fig. 7.1
The vertical sides of the coil have a length of 5.00 cm and the horizontal sides have a length of 3.00 cm . The initial reading on the newton meter is 0.563 N .
A U-shaped magnet rests on a top-pan balance that is set to a reading of 0.00 g . The lower edge of the coil is lowered into the region between the poles of the U-shaped magnet, as shown in the side view in Fig. 7.2.
Fig. 7.2
The magnetic field in the region between the poles is uniform.
The lower edge of the coil is entirely within the uniform magnetic field.
A current of 3.94 A is now passed through the coil. This causes the reading on the top-pan balance to change to 2.16 g .
Explain why the current causes a vertical force to act on the coil.
Determine, to three significant figures, the flux density B of the uniform magnetic field.
Determine what is now the reading on the newton meter. Explain your reasoning.