Q7852.A $3000 \mathrm{W}$ electric cooker is to be used on a $200 \mathrm{V}$ mains circuit. Which of the fuses below can be used safely with the cooker?
A$2 \mathrm{A}$
B$5 \mathrm{A}$
C$10 \mathrm{A}$
D$20 \mathrm{A}$
Correct Answer: D
$I = \dfrac{P}{V} = \dfrac{3000}{200} = 15 \mathrm{A}$. A $20 \mathrm{A}$ fuse is safe.
JAMB (UTME)
Physics
1998
Q7853.A galvanometer has a resistance of $5 \Omega$. By using a shunt wire of resistance $0.05 \Omega$, the galvanometer could be converted to an ammeter capable of reading $2 \mathrm{A}$. What is the current through the galvanometer?
Q7854.In the diagram above, if the internal resistance of the cell is zero, the ratio of the power $P_1$ and $P_2$ dissipated by $R_1$ and $R_2$ respectively, is
A$\dfrac{R_2}{R_1}$
B$\dfrac{R_1}{R_2}$
C$\dfrac{R_1 + R_2}{R_2}$
D$\dfrac{R_1 + R_2}{R_1}$
Correct Answer: A
In parallel, $P = \dfrac{V^2}{R}$, so $P \propto \dfrac{1}{R}$. $\dfrac{P_1}{P_2} = \dfrac{R_2}{R_1}$.
JAMB (UTME)
Physics
1998
Q7855.If $\Delta x$ is the uncertainty in the measurement of the position of a particle along the x-axis and $\Delta P_x$ is the uncertainty in the measurement of the linear momentum along the x-axis, then the uncertainty principle relation is given as
A$\Delta x \Delta P_x > h$
B$\Delta x \Delta P_x = 0$
C$\Delta x \Delta P_x < h$
D$\Delta x \Delta P_x \geq \dfrac{h}{4\pi}$
Correct Answer: D
Heisenberg's uncertainty principle: $\Delta x \Delta P_x \geq \dfrac{h}{4\pi}$.
JAMB (UTME)
Physics
1998
Q7856.$^{23}_{11}\mathrm{Na} + \text{Proton} \rightarrow X + \text{alpha particle}$. What are the values of p and q respectively in the equation above?
A$10$ and $20$
B$12$ and $24$
C$20$ and $10$
D$24$ and $12$.
Correct Answer: C
$^{23}_{11}\mathrm{Na} + ^1_1\mathrm{H} \rightarrow ^A_Z\mathrm{X} + ^4_2\mathrm{He}$. Mass: $23 + 1 = A + 4 \Rightarrow A = 20$. Atomic: $11 + 1 = Z + 2 \Rightarrow Z = 10$. So X is $^{20}_{10}\mathrm{X}$.
JAMB (UTME)
Physics
1998
Q7857.A semi-conductor diode is used in rectifying alternating current into direct current mainly because it
AAllows current to flow in either direction
BIs non-linear
COffers a high input resistance
DAllows current to flow only in one direction.
Correct Answer: D
A diode conducts in one direction only.
JAMB (UTME)
Physics
1998
Q7858.In semi-conductors, the carriers of current at room temperature are
AElectrons only
BElectrons and holes
CHoles only
DElectrons and ions
Correct Answer: B
In semiconductors, current is carried by both electrons and holes.
JAMB (UTME)
Physics
1998
Q7859.What is the speed of a particle of mass $10^{-7} \mathrm{kg}$ whose wavelength is $10^{-8} \mathrm{m}$?
A$6.63 \mathrm{ms}^{-1}$
B$66.30 \mathrm{ms}^{-1}$
C$663.00 \mathrm{ms}^{-1}$
D$6630.00 \mathrm{ms}^{-1}$
Correct Answer: A
$\lambda = \dfrac{h}{mv}$. $v = \dfrac{h}{m\lambda} = \dfrac{6.63 \times 10^{-34}}{10^{-7} \times 10^{-8}} = \dfrac{6.63 \times 10^{-34}}{10^{-15}} = 6.63 \times 10^{-19} \mathrm{ms}^{-1}$. The answer key A is incorrect.
JAMB (UTME)
Physics
1998
Q7860.In a series R-L-C circuit at resonance, the voltages across the resistor and the inductor are $30 \mathrm{V}$ and $40 \mathrm{V}$ respectively. What is the voltage across the capacitor?
A$30 \mathrm{V}$
B$40 \mathrm{V}$
C$50 \mathrm{V}$
D$70 \mathrm{V}$
Correct Answer: B
At resonance, $V_C = V_L = 40 \mathrm{V}$.
JAMB (UTME)
Physics
1998
Q7861.Gamma rays are produced when
AHigh velocity electrons are abruptly stopped in metals
BEnergy changes occur within the nucleus of atoms
CEnergy changes occur within the electronic structure of atoms
DElectrons are deflected in very strong magnetic fields.
Correct Answer: B
Gamma rays are produced by energy changes within the nucleus.
JAMB (UTME)
Physics
1998
Q7862.In the Rutherford scattering experiment, a beam of alpha particles was fired at a thin gold film with some of the particles being considerably deflected. This shows that
AA gold nucleus contains protons, neutrons and electrons uniformly distributed in a tiny volume.
BThe gold nucleus is positively charged and is concentrated in a tiny volume.
CThe gold nucleus emitted alpha particles
DThe gold nucleus is concentrated in a tiny volume and contains alpha particles.
Correct Answer: B
The deflection of alpha particles shows that the nucleus is positively charged and concentrated in a tiny volume.
JAMB (UTME)
Physics
1998
Q7863.A catapult used to hold a stone of mass $500 \mathrm{g}$ is extended by $20 \mathrm{cm}$ with an applied force F. If the stone leaves with a velocity of $40 \mathrm{ms}^{-1}$, the value of F is
Q7865.A lead bullet of mass $0.05 \mathrm{kg}$ is fired with a velocity of $200 \mathrm{ms}^{-1}$ into a lead block of mass $0.95 \mathrm{kg}$. Given that the lead block can move freely, the final kinetic energy after impact is
Q7866.A ball of mass $0.1 \mathrm{kg}$ is thrown vertically upwards with a speed of $10 \mathrm{ms}^{-1}$ from the top of a tower $10 \mathrm{m}$ high. Neglecting air resistance, its total energy just before hitting the ground is $[g = 10 \mathrm{ms}^{-2}]$
A$5 \mathrm{J}$
B$10 \mathrm{J}$
C$15 \mathrm{J}$
D$20 \mathrm{J}$
Correct Answer: C
Total energy $= PE + KE = mgh + \dfrac{1}{2}mv^2 = 0.1 \times 10 \times 10 + \dfrac{1}{2} \times 0.1 \times 10^2 = 10 + 5 = 15 \mathrm{J}$.
JAMB (UTME)
Physics
1999
Q7867.The figure above represents a frictionless pulley system in which a weight W is in equilibrium with a weight of $40 \mathrm{N}$. Find the value of W.
A$13.1 \mathrm{N}$
B$20.0 \mathrm{N}$
C$40.0 \mathrm{N}$
D$80.0 \mathrm{N}$
Correct Answer: D
The pulley system has a velocity ratio of 2. For equilibrium, $W = 2 \times 40 = 80 \mathrm{N}$.
JAMB (UTME)
Physics
1999
Q7868.The diagram above shows a solid figure with base PQ and centre of gravity G on an inclined plane. Which of the following statements is correct?
AThe solid will fall over if the vertical line through G lies outside the base.
BThe solid will fall over if the vertical line through G lies inside the base.
CThe solid will not fall over if the vertical line through G lies outside the base.
DThe solid can never fall over.
Correct Answer: A
A body topples when the vertical line through its centre of gravity falls outside its base.
JAMB (UTME)
Physics
1999
Q7869.Two bodies have masses in the ratio $3:1$. They experience forces which impart to them accelerations in the ratio $2:9$ respectively. Find the ratio of the forces the masses experience.
A$1:4$
B$2:1$
C$2:3$
D$2:5$
Correct Answer: C
$F = ma$. $\dfrac{F_1}{F_2} = \dfrac{m_1 a_1}{m_2 a_2} = \dfrac{3}{1} \times \dfrac{2}{9} = \dfrac{6}{9} = \dfrac{2}{3}$. Ratio is $2:3$.
JAMB (UTME)
Physics
1999
Q7870.The diagram above shows the velocity-time graph of a vehicle. Its acceleration and retardation respectively are
Q7871.A particle of mass $10^{-2} \mathrm{kg}$ is fixed to the tip of a fan blade which rotates with angular velocity of $100 \mathrm{rads}^{-1}$. If the radius of the blade is $0.2 \mathrm{m}$, the centripetal force is
Q7872.The inner diameter of a small test tube can be measured accurately using a
AMicrometer screw gauge
BPair of dividers
CMetre rule
DPair of vernier calipers.
Correct Answer: D
Vernier calipers can measure internal dimensions accurately.
JAMB (UTME)
Physics
1999
Q7873.A gas at a volume $V_0$ in a container at pressure $P_0$ is compressed to one-fifth of its volume. What will be its pressure if it maintains its original temperature T?
Q7874.A piece of substance of specific heat capacity $450 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$ falls through a vertical distance of $20 \mathrm{m}$ from rest. Calculate the rise in temperature of the substance on hitting the ground when all its energies are converted into heat. $[g = 10 \mathrm{ms}^{-2}]$
Q7875.The diagram above shows a lift pump with valves at P and Q. During a downward stroke of the piston,
ABoth valves are open
BP is open while Q is closed
CP is closed while Q is open
DBoth valves are closed.
Correct Answer: B
During a downward stroke, the piston moves down, valve P opens and Q closes.
JAMB (UTME)
Physics
1999
Q7876.In the J-tube above, Y and X are on the same horizontal level and $30 \mathrm{cm}^3$ of air is trapped above Y when the atmospheric pressure is $75 \mathrm{cm}$ Hg. Calculate the volume of air trapped above Y when $15 \mathrm{cm}$ Hg is now poured into the limb above X.
Q7877.If the stress on a wire is $10^7 \mathrm{Nm}^{-2}$ and the wire is stretched from its original length of $10.00 \mathrm{cm}$ to $10.05 \mathrm{cm}$. The Young's modulus of the wire is
Q7878.A solid weighs $10.0 \mathrm{N}$ in air, $6.0 \mathrm{N}$ when fully immersed in water and $7.0 \mathrm{N}$ when fully immersed in a certain liquid X. Calculate the relative density of the liquid.
A$\dfrac{5}{3}$
B$\dfrac{4}{3}$
C$\dfrac{3}{4}$
D$\dfrac{7}{10}$
Correct Answer: C
Relative density $= \dfrac{\text{Weight loss in liquid}}{\text{Weight loss in water}} = \dfrac{10 - 7}{10 - 6} = \dfrac{3}{4}$.
JAMB (UTME)
Physics
1999
Q7879.I. A liquid boils when its saturated vapour pressure is equal to the external pressure.
AI, II and III
BI, II, III and IV
CI, II and IV
DII, III and IV.
Correct Answer: A
Statements I, II, and III are correct. Statement IV is incorrect.
JAMB (UTME)
Physics
1999
Q7880.When the temperature of a liquid is increased, its surface tension
ADecreases
BIncreases
CRemains constant
DIncreases then decreases.
Correct Answer: A
Surface tension decreases with increasing temperature.
JAMB (UTME)
Physics
1999
Q7881.When the brakes in a car are applied, the frictional force on the tyres is
AA disadvantage because it is in the direction of motion of the car
BA disadvantage because it is in the opposite direction of motion of the car.
CAn advantage because it is in the direction of motion of the car.
DAn advantage because it is in the opposite direction of motion of the car.
Correct Answer: D
Friction on the tyres opposes motion, which is advantageous for stopping the car.
JAMB (UTME)
Physics
1999
Q7882.The lowest note emitted by a stretched string has a frequency of $400 \mathrm{Hz}$. How many overtones are there between $40 \mathrm{Hz}$ and $180 \mathrm{Hz}$?
A4
B3
C2
D1
Correct Answer: B
The overtones are $800, 1200, 1600, \ldots$ None are between $40$ and $180$. The answer key B is incorrect. (Note: This question is flawed).
JAMB (UTME)
Physics
1999
Q7883.A man stands $4 \mathrm{m}$ in front of a plane mirror. If the mirror is moved $1 \mathrm{m}$ towards the man, the distance between him and his image is
A$3 \mathrm{m}$
B$5 \mathrm{m}$
C$6 \mathrm{m}$
D$10 \mathrm{m}$
Correct Answer: C
New distance from mirror $= 4 - 1 = 3 \mathrm{m}$. Image distance $= 3 \mathrm{m}$. Total distance $= 3 + 3 = 6 \mathrm{m}$.
JAMB (UTME)
Physics
1999
Q7884.If a sound wave goes from a cold-air region to a hot-air region, its wavelength
AIncreases
BDecreases
CDecreases then increases
DRemains constant
Correct Answer: A
Velocity increases in hot air, so wavelength increases ($v = f\lambda$).
JAMB (UTME)
Physics
1999
Q7885.The inside portion of part of a hollow metal sphere of diameter $20 \mathrm{cm}$ is polished. The portion will therefore form a
AConcave mirror of focal length $5 \mathrm{cm}$
BConcave mirror of focal length $10 \mathrm{cm}$
CConvex mirror of focal length $5 \mathrm{cm}$
DConvex mirror of focal length $20 \mathrm{cm}$
Correct Answer: A
The polished inner surface forms a concave mirror. $f = \dfrac{R}{2} = \dfrac{10}{2} = 5 \mathrm{cm}$.
JAMB (UTME)
Physics
1999
Q7886.The equation of a wave traveling along the positive x-direction is given by $y = 0.25 \times 10^{-3} \sin(500t - 0.025x)$. Determine the angular frequency of the wave motion.
A$0.25 \times 10^{-3} \mathrm{rads}^{-1}$
B$0.25 \times 10^{-1} \mathrm{rads}^{-1}$
C$5.00 \times 10^2 \mathrm{rads}^{-1}$
D$2.50 \times 10^2 \mathrm{rads}^{-1}$
Correct Answer: C
Comparing with $y = A\sin(\omega t - kx)$, $\omega = 500 = 5.00 \times 10^2 \mathrm{rads}^{-1}$.
JAMB (UTME)
Physics
1999
Q7887.Calculate the mass of ice that would melt when $2 \mathrm{kg}$ of copper is quickly transferred from boiling water to a block of ice without heat loss. [Specific heat capacity of copper $= 400 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$; Latent heat of fusion of ice $= 3.3 \times 10^5 \mathrm{Jkg}^{-1}$]
A$\dfrac{8}{33} \mathrm{kg}$
B$\dfrac{33}{80} \mathrm{kg}$
C$\dfrac{80}{33} \mathrm{kg}$
D$\dfrac{33}{8} \mathrm{kg}$
Correct Answer: A
Heat lost by copper $= 2 \times 400 \times 100 = 80000 \mathrm{J}$. Mass of ice melted $= \dfrac{80000}{3.3 \times 10^5} = \dfrac{8}{33} \mathrm{kg}$.
JAMB (UTME)
Physics
1999
Q7888.The diagram above represents a transverse electromagnetic wave traveling with speed $3.0 \times 10^8 \mathrm{ms}^{-1}$. What is the frequency of the wave?
A$3.0 \times 10^7 \mathrm{Hz}$
B$90 \times 10^7 \mathrm{Hz}$
C$1.0 \times 10^9 \mathrm{Hz}$
D$3.0 \times 10^9 \mathrm{Hz}$
Correct Answer: C
From the diagram, wavelength $\lambda = 0.3 \mathrm{m}$. $f = \dfrac{v}{\lambda} = \dfrac{3.0 \times 10^8}{0.3} = 1.0 \times 10^9 \mathrm{Hz}$.
JAMB (UTME)
Physics
1999
Q7889.The temperature gradient across a copper rod of thickness $0.02 \mathrm{m}$, maintained at two temperature junctions of $20^{\circ}\mathrm{C}$ and $80^{\circ}\mathrm{C}$ respectively is
Q7890.The diagram above shows a magnet X with its South pole moved along a soft-iron bar PQ in the direction shown. After some time, the poles at P and Q respectively are
ANorth-North
BNorth-South
CSouth-North
DSouth-South
Correct Answer: B
The end near the S-pole becomes N, so P is N. The far end Q is S.
JAMB (UTME)
Physics
1999
Q7891.Four cells each of e.m.f. $1.5 \mathrm{V}$ and internal resistance of $4 \Omega$ are connected in parallel. What is the effective e.m.f. and internal resistance of the combination?
A$6.0 \mathrm{V}$, $16 \Omega$
B$6.0 \mathrm{V}$, $1 \Omega$
C$1.5 \mathrm{V}$, $4 \Omega$
D$1.5 \mathrm{V}$, $1 \Omega$
Correct Answer: D
For cells in parallel, effective e.m.f. $= 1.5 \mathrm{V}$. Internal resistance $= \dfrac{4}{4} = 1 \Omega$.
JAMB (UTME)
Physics
1999
Q7892.In the circuit above, the ammeter reads a current of $5.0 \mathrm{A}$ when $R = 8 \Omega$ and reads $7.0 \mathrm{A}$ when $R = 5 \Omega$. The value of the unknown resistance X is
Q7893.An astronomical telescope is said to be in normal adjustment when the
AEye is accommodated
BFocal length of objective lens is longer than that of eye piece
CFinal image is at the near point of eye
DFinal image is at infinity.
Correct Answer: D
In normal adjustment, the final image is at infinity.
JAMB (UTME)
Physics
1999
Q7894.Steel is more suitable for permanent magnet than iron because the former
AIs easily demagnetized by shaking vigorously
BIs an alloy of many metals
CIs easily magnetized by alternating current through one cycle
DRetains magnetism more than iron.
Correct Answer: D
Steel retains magnetism better than iron.
JAMB (UTME)
Physics
1999
Q7895.The diagram above shows the prism arrangement in a
ABinocular
BSpectrometer
CPeriscope
DProjector
Correct Answer: C
The prism arrangement shown is for a periscope.
JAMB (UTME)
Physics
1999
Q7896.The velocities of light in air and glass are $3.0 \times 10^8 \mathrm{ms}^{-1}$ and $2.0 \times 10^8 \mathrm{ms}^{-1}$ respectively. If the angle of refraction is $30^{\circ}$, the sine of the angle of incidence is
Q7897.In the series a.c. circuit shown above, the p.d across the inductor is $8 \mathrm{V}$ r.m.s. and across the resistor is $6 \mathrm{V}$ r.m.s. The effective voltage is