2009 - WAEC Physics Past Questions and Answers - page 4
31
Sound interference is necessary to produce the phenomenon of
A
beats
B
doppler effect
C
acoustic resonance
D
echo
correct option: a
Users' Answers & Comments32
A satellite in circular motion around the earth does not have
A
a gravitational force acting on it
B
a uniform velocity
C
an acceleration
D
a centripetal force acting on it
correct option: b
Users' Answers & Comments33
When a conductor mounted on an insulating stand is charged and left for sometime, the conductor eventually loses all its charges. This is because the
A
electric charges evaporate from the surface of the conductor
B
charges are connected to earth
C
charges on the conductor are neutralized by opposite charges from the surrounding air
D
charges ionize the surrounding air
correct option: c
Users' Answers & Comments34
An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, Er. A test charge is placed at a point p, distance r from the surface of the sphere. Let Eo represent the permitivity of free space. The electric potential at p is given by the expression
A
\(\frac{Q}{4 \pi E_o E_r}\)
B
\(\frac{Q}{4 \pi E_o E_r (R +r)}\)
C
\(\frac{Q}{4 \pi E_o E_r(R - r)}\)
D
\(\frac{Q}{4 \pi E_o E_rR}\)
correct option: d
Users' Answers & Comments35
An isolated metal sphere of radius R, carrying an electric charge Q, is situated in the medium of relative permitivity, Er. A test charge is placed at a point p, distance r from the surface of the sphere. Let Eo represent the permitivity of free space. The magnitude of the electric field intensity at P is given by the expression
A
\(\frac{Q}{4 \pi E_o E_r r^2}\)
B
\(\frac{Q}{4 \pi E_o E_r(R + r)^2}\)
C
\(\frac{Q}{4 \pi E_o E_r(R - r)^2}\)
D
\(\frac{Q}{4 \pi E_o E_rR^2}\)
correct option: d
Users' Answers & Comments36
A resistor of resistance R is connected to a battery of negligible internal resistance. If a siilar resistor is connected in series with it the
A
effective resistance of the circuit is halved
B
total power dissipated is doubled
C
total current in the circuit is halved
D
terminal voltage is halved
correct option: b
Users' Answers & Comments37
A cell of e.m.f. 1.5V is connected in series with a resistor of resistance 3.0\(\Omega\). A voltmeter connected across the cell registers 0.9V. Calculate the internal resistance of the cell
A
2.0\(\Omega\).
B
3.0\(\Omega\).
C
5.0\(\Omega\).
D
6.0\(\Omega\).
correct option: a
(\frac{V}{R} = \frac{E}{R + r})
(\frac{0.9}{3} = \frac{1.5}{3 + r})
r = 2(\Omega).
38
A wire of resistivity 4.40 x 10-5\(\Omega\) cm has a cross sectional area of 7.50 x 10-4 cm2. Calculate the length of the wire that will be required to make a 4.0\(\Omega\) resistor
A
82.50 cm
B
68.18cm
C
15.90cm
D
11.95cm
correct option: b
L = (\frac{R.A}{e} = \frac{4 \times 7.50 \times 106{-4}}{4.40 \times 10^{-5}} = 68.18cm)
Users' Answers & Comments39
A battery of e.m.f. 12.0V and internal resistance0.5\(\Omega\) is connected to 1.5\(\Omega\) and 4.0\(\Omega\) series resistor. Calculate the terminal voltage of the battery.
A
13.0V
B
11.0V
C
3.0V
D
1.0V
correct option: b
(\frac{V}{R} = \frac{E}{R + r} = \frac{V}{5.5} = \frac{12}{6})
v = 11.0V
40
If the direction of the curent in a straight wire is reversed, the magnetic field
A
remains the same
B
becomes parallel to the wire
C
ceases to exist
D
is oppositely directed
correct option: d
Users' Answers & Comments