Electromagnetic field questions and answers (physics)


Electromagnetic field

1. What is electromagnetic field?

Answer: Electromagnetic field is region where both electric force and magnetic force are felt by   charged particles.

2. What is the total force of electromagnetic field?

Answer: the total force F of electromagnetic field is given by the vector sum of electric and magnetic forces. Fe and Fm respectively. That is

F = Fe + Fm

F = q(E + v  x B)

3. The force experienced by a current carrying conductor of length 100cm is 2.0N. Calculate the current in the conductor if it is flowing in 450 direction, with the field of 1.0 tesla.

Answer: Using F = BILsinѲ

Where F = Force =2.0N, B=Magnetic flux density of the field = 1.0 tesla or 1.0T Ѳ =450, L = length of the conductor = 100cm =1m

Therefore F= BILsinѲ   is given as

2 = 1 x 1 x I x sin450

I = 2/sin450 =2.83A

The current = 2.83A.

4. Calculate the force on a charge +2ɥC moving with a velocity  2 x 106m/s in a field of magnetic flux density 0.5T

(i). For Parallel field

(ii) For perpendicular field

Answer: Using   

F = qvBsinѲ,

where q = charges = +2ɥC, V= velocity of the charge in the field = 2 x 106m/s, B = magnetic flux density = 0.5T, Ѳ = 900 for perpendicular field and Ѳ = 00 for parallel field.

So for (i).  Parallel field is given as

F = 2 x 10-6 x 2 x 106 x 0.5 x sin0 = 0 since Ѳ = 0 for parallel field

For (ii) Perpendicular field

F = 2 x 10-6 x 2 x 106 x 0.5 x sin90 

F = 2 x 10-6 + 6 x 0.5 x 1

F = 2 x 10 x 0.5

F = 20 x 0.5 = 2N

So for (ii) Perpendicular field F = 2N

5. What is magnetic flux?

Answer: The magnetic flux is the line of force of magnetic field. The unit is webers (Wb). It is given as

Φ = ABcosѲ, where   Φ = magnetic flux, A =area of the surface at right angles to the field,  B  = magnetic flux density.

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