d. The current flows clockwise initially, and then it 1loW stopping concentrated

Question

d. The current flows clockwise initially, and then it 1loW stopping concentrated in circular area (think about inside of solenoid). Direction of induced electric field from your point of view is: 7. Uniform magnetic field pointing towards you and decreasing in magnitude is a. Clockwise b. Counterclockwise c. Zero d. Points from the center of circular area. e. Points towards the center of circular area. 8. Uniform electric field pointing towards you and decreasing in magnitude is concentrated in circular area (think about field inside of capacitor). Direction of induced magnetic field from your point of view is: a. Clockwise b. Counterclockwise c. Zero d. Points from the center of circular area. e. Points towards the center of circular area. If the magnetic field in traveling EM wave at some instant is in x direction, and electric field at the same instant is in y-direction, this wave travels in 9. a. Positive x direction b. Negative x direction c. Positive y direction d. Negative y direction. Positive z direction e. t Negative z direction 10. Which of the following correctly lists electromagnetic waves in order from longest to shortest wavelength? rays, ultraviolet, infrared, microwaves a. gamma b. microwaves, ultraviolet, visible light, gamma rays c. radio waves, infrared, gamma rays, ultrav olet d. television, infrared, visible light, X-rays II. Solenoid A has total numher of

Explanation / Answer

a) We can use Lenz law and right hand rule to find the direction of the induced electric field

When a magnet is moving towards the coil or solenoid , an induced current appears in it in anti clockwise direction.

When the magnet is moving away from the coil ( field is decreasing ) induced current appears in clockwise direction.

Since magnetic forces do not do any work , current is due to the induced electric field which must be in clockwise direction to push the electrons to produce induced current.

So answer is option ( a ) clockwise

B) When the electric field through a loop is changing , it indicates that flux is also changing. This changing electric flux produces an induced magnetic field around the loop.

This magnetic field will have same magnitude at every point around the loop and will have circular symmetry .

Direction of induced magnetic field can be found using the right hand rule similar to induced electric field.

When the charge or electric field of capacitor increases , induced magnetic field will be in counter clockwise direction.

When the electric field is decreasing, induced magnetic field will be along clockwise direction.

So answer to question 8 is option ( a ) clockwise

C)When the electric field is pointing along positive X axis and magnetic field along the positive Y axis , EM wave travels along positive Z axis.

We can find it by using right hand rule for product of vectors.

Direction of E × B is in positive Z direction

But here magnetic field is along X axis and electric field is along Y axis.

So we are multiplying in reverse order , resultant direction also reverses.

B × E = - E × B

So the resultant direction of the EM wave will be along negative Z axis.

So answer is option ( f ) negative Z direction.

D) Electro magnetic spectrum consists of following waves in descending order according to their wavelengths.

Radio waves ( tv waves ) , micro waves , infrared waves , visible rays , ultraviolet waves , X rays and Gamma rays

So the answer to question 10 is ( d ) television,infrared , visible and X rays

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