Magnetism

Calculate the magnetic field at a point, P, 5 cm from a wire carrying a current of 20 A to the left.

• 80 mT into the page

• 0.0004 T into the page

• 80 mT out of the page

• 0.0004 T out of the page

What is the magnetic field at position X, 0.15 m below wire A and 0.1 m above wire B, given that wire A carries a current of 1.5A to the right and wire B carries 2.5 A to the right.

• 3.0 x 10^-6 T into the page

• 3.0 x 10^-6 T out of the page

• 7 x 10^-6 T into the page

• 5.2 x 10^-6 T out of the page

A 3.0 A current flows in a wire of length 15 cm in a magnetic field of strength  $50\ \mu T$ . Calculate the magnitude of the force on the wire if the wire makes an angle of  $55\degree$  to the field.

• 3.2 N

•  $2.25\times10^{-5}N$  

• 1,800 N 

•  $1.8\times10^{-5}N$  

A wire of length 50 cm and mass 10 g is suspended in a horizontal plane by a pair of flexible leads. The wire is in a magnetic field of magnitude 0.50 T, which is directed as shown. What current is needed to remove the tension in the supporting leads?

• 16 A to the right

• 4.0 A to the left

• 25 mA to the left

• 0.39 A to the right

Magnetic field vectors point

• From North to South pole

• From South to North Pole

• Outwards from the magnet

• Inwards to the magnet

What is the rule used to determine the direction of the force which acts on a current-carrying wire in a magnetic field?

• Fleming's left hand rule

• Coulomb's right hand rule

• Lenz's rule

• Faraday's rule

The magnetic flux is a measurement of the total magnetic field, or number of field lines, that passes through a given area, which 

• is represented by $\phi$  and has SI units of Tesla

• is represented by  $\mu_o$   and has SI units of Weber

• is represented by B and has SI units of Tesla

• is represented by $\phi$  and has SI units of Weber

The magnetic flux density is a measure of the strength of the magnetic field, or the number of magnetic field lines per unit area, which

• is represented by $\phi$  and has SI units of Tesla

• is represented by  $\mu_o$   and has SI units of Weber

• is represented by B and has SI units of Tesla

• is represented by $\phi$  and has SI units of Weber

Which direction is the North Pole of this electromagnet?

• Right
• Left
• Up
• Down

What causes magnetism?

• the sun

• moving neutrons

• moving charges

• friction