If a wire coil has 10 turns and carries 500 mA of current, what is the magnetomotive force in ampere-turns?
5.0
Which of the following is not generally observed in a geomagnetic storm?
Disruption of microwave propagation
A device that reverses magnetic field polarity to keep a dc motor rotating is
a commutator
When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage
increases
The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is
2,000 V
For a given wirewound core, an increase in current through the coil
increases the flux density
If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density
decreases
When the current through the coil of an electromagnet reverses,
direction of the magnetic field reverses
What is the reluctance of a material that has a length of 0.07 m, a cross-sectional area of 0.014 m2, and a permeability of 4,500
Wb/At
× m?
1111 At/Wb
A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will
decrease
What is the flux density when the flux is 5.5
Wb
and the cross-sectional area is 6 × 10–3m2?
917 µT
If the steel disk in a crankshaft position sensor has stopped with the tab in the magnet's air gap, the induced voltage
is zero
What is the flux density in a magnetic field in which the flux in 0.1 m2is 600
Wb?
6,000 µT
A ball is thrown upward. While the ball is in free fall, does its acceleration
Remain constant
After a ball is thrown upward and is in the air, its speed in all path
Decreases and then increases
If vector b is added to vector a, which two of the following choices must be true in order for the resultant vector to be equal to zero?
A nd B are parallel in the same direction and have same magnitude
A car moves along y-axes. In the figure, velocity of the car as a function of time is shown in three parts (I, II, III). Which statement is ALWAYS true?
Velocity is constant in part II
of two vectors A and B, if the angle between them is 30 degree, and magnitudes are |A|=4, |B|=2
4
When a box rests on the floor, it is acted upon by the gravitational and the _________________ force.
Normal
Motion is produced by
unbalanced forces
Force is that agent which produces or tends to produce the __________.
Acceleration in the body
A force of 3N acts perpendicularly to a force of 4N. Their resultant has magnitude of ______
5N
In inelastic collision between the two bodies __________.
Only momentum of the system is conserved
Work done by a grass cutter is maximum when he pulls it __________.
Making an angle 900with the floor
A man does the work if he ___________.
Goes to fifth floor of the building