# 2016 - WAEC Physics Past Questions and Answers - page 5

41
A 10$$\mu$$C charge moves with a velocity of 1.0 x 105 ms-1 at right angle to a uniform magnetic field of flux density 5.0 x 10-4T. Calculate the force on the charge
A
5.0 x 10-5N
B
5.0 x 10-4N
C
5.0 x 105N
D
5.0 x 106N
correct option: b
F = qvB

= 10 x 10-6 x 1.0 x 105 x 10-4

= 5.0 x 10-4N
42
Which of the following statements is not correct about steel and soft iron?
A
steel is more magnetized than soft iron
B
permanent magnets are usually made of steel
C
soft iron is more readily magnetized than steel
D
soft iron more readily loses its magnetism than steel
correct option: a
43
What determines the polarity at the ends of an electromagnet? The
A
magnitude of the current passing through the wire
B
material of the core of the magnet
C
material of the coil
D
direction of current in the wire
correct option: d
44
How many beta particle(s) are emitted in the radioactive decay of $$^{198}_{79}Au \leftarrow ^{198}_{80}Hg$$?
A
1
B
2
C
3
D
5
correct option: a
45
The phenomenon by which two light atomic nuclear combine to form a heavy nuclide with the release of energy is known as
A
B
nuclear fusion
C
nuclear fission
D
chain reaction
correct option: b
46
In a p-type semiconductor, the
A
number of holes are equal to the number of electrons
B
electrical resistivity increases
C
electrons are the majority charge carriers
D
holes are the majority charge carriers
correct option: d
Let $$\Delta$$x be the uncertainty in the measurements of position and $$\Delta$$p the uncertainty in measurement of momentum. The uncertainty principle relation is given as
$$\Delta$$x . $$\Delta$$p = h
$$\Delta$$x . $$\Delta$$p $$\leq$$ = h
$$\Delta$$x . $$\Delta$$p $$\geq$$ = h
$$\Delta$$x . $$\Delta$$p > h