Q7902.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
1999
Q7903.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?
Q7904.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
1999
Q7905.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
1999
Q7906.$^{23}_{11}\mathrm{Na} + \text{Proton} \rightarrow X + \text{alpha particle}$. 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
1999
Q7907.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
1999
Q7908.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
1999
Q7909.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
1999
Q7910.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
1999
Q7911.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
1999
Q7912.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
1999
Q7913.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
Q7914.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
Q7915.A hand bag containing some load weighing $162 \mathrm{N}$ is carried by two students each holding the handle of the bag next to him. If each handle is pulled at $60^{\circ}$ to the vertical, find the force on each student's arm.
Q7916.I. The frictional force is independent of the area of the surfaces in contact.
AI, II and IV
BI, II and III
CI, III and IV
DII, III and IV.
Correct Answer: A
Sliding friction is independent of area and speed, but depends on the nature of surfaces and is proportional to the normal reaction.
JAMB (UTME)
Physics
2000
Q7917.When a ship sails from salt water into fresh water, the fraction of its volume above the water surface will
ARemain the same
BIncrease
CDecrease
DIncrease then decrease.
Correct Answer: B
Fresh water is less dense than salt water, so the ship sinks deeper, reducing the volume above water. The answer key B is incorrect; the correct answer is C.
JAMB (UTME)
Physics
2000
Q7918.A simple pendulum has a period of $17.0 \mathrm{s}$. When the length is shortened by $1.5 \mathrm{m}$ its period is $8.5 \mathrm{s}$. Calculate the original length of the pendulum.
Q7922.If the force and the velocity on a system are each reduced simultaneously by half, the power of the system is
ADoubled
BConstant
CReduced to a quarter
DReduced by half.
Correct Answer: C
$P = Fv$. New power $= \dfrac{F}{2} \times \dfrac{v}{2} = \dfrac{Fv}{4} = \dfrac{P}{4}$.
JAMB (UTME)
Physics
2000
Q7923.The velocity ratio of a machine is 5 and its efficiency is $75\%$. What effort would be needed to lift a load of $150 \mathrm{N}$ with the machine?
Q7924.A rope is being used to pull a mass of $10 \mathrm{kg}$ vertically upward. Determine the tension in the rope if, starting from rest, the mass acquires a velocity of $4 \mathrm{ms}^{-1}$ in $8 \mathrm{s}$. $[g = 10 \mathrm{ms}^{-2}]$
Q7925.A stream is flowing at $0.75 \mathrm{ms}^{-1}$ and a boat heading perpendicular to the stream landed at the opposite bank at an angle $30^{\circ}$. Calculate the velocity of the boat.
A$0.65 \mathrm{ms}^{-1}$
B$0.86 \mathrm{ms}^{-1}$
C$1.00 \mathrm{ms}^{-1}$
D$1.50 \mathrm{ms}^{-1}$
Correct Answer: D
$\tan 30^{\circ} = \dfrac{v_{stream}}{v_{boat}}$. $v_{boat} = \dfrac{0.75}{\tan 30^{\circ}} = \dfrac{0.75}{0.577} = 1.30 \mathrm{ms}^{-1}$. The answer key D is incorrect.
JAMB (UTME)
Physics
2000
Q7926.I. Coherence
AI, II and III
BI, II and III
CI, II and IV
DII and III.
Correct Answer: A
Coherence, same frequency, and same wavelength are necessary for interference.
JAMB (UTME)
Physics
2000
Q7927.An engineer intends to deviate a light ray from its path by $120^{\circ}$ through reflection from a plane mirror. Calculate the angle of incidence.
Q7928.The readings above are for three consecutive days from a wet and dry bulb hygrometer. It can be concluded that the relative humidity for the three days
AIncreased steadily
BRemained unchanged
CWas least on day 1
DDecreased steadily
Correct Answer: C
The difference between dry and wet bulb readings was greatest on day 1, so relative humidity was least on day 1.
JAMB (UTME)
Physics
2000
Q7929.Total internal reflection occurs when light moves from
AAir to water
BWater to glass
CA dense medium to a less dense medium
DA less dense medium to a dense medium
Correct Answer: C
Total internal reflection occurs when light travels from a denser to a less dense medium.
JAMB (UTME)
Physics
2000
Q7930.One end of a long wire is fixed while a vibrator is attached to the other end. When the vibrator is energized, the types of waves generated in the wire are
AStationary and transverse
BProgressive
CStationary and longitudinal
DProgressive and longitudinal.
Correct Answer: A
The vibrator generates transverse waves which reflect to form stationary waves.
JAMB (UTME)
Physics
2000
Q7931.A sonometer wire is vibrating at frequency $f_0$. If the tension in the wire is doubled while the length and the mass per unit length are kept constant, the new frequency of vibration is
A$\dfrac{f_0}{2}$
B$2f_0$
C$\dfrac{f_0}{\sqrt{2}}$
D$f_0\sqrt{2}$
Correct Answer: D
$f \propto \sqrt{T}$. $f_{new} = f_0\sqrt{2}$.
JAMB (UTME)
Physics
2000
Q7932.A boy observes a piece of stone at the bottom of a river $6.0 \mathrm{m}$ deep. If he looks from the surface of the river, what is the apparent distance of the stone from him?
Q7933.A metal of mass $0.5 \mathrm{kg}$ is heated to $100^{\circ}\mathrm{C}$ and then transferred to a well-lagged calorimeter of heat capacity $80 \mathrm{JK}^{-1}$ containing water of heat capacity $420 \mathrm{JK}^{-1}$ at $15^{\circ}\mathrm{C}$. If the final steady temperature of the mixture is $25^{\circ}\mathrm{C}$, find the specific heat capacity of the metal.
A$92 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$
B$133 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$
C$286 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$
D$887 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$
Correct Answer: D
Heat lost by metal $=$ Heat gained by calorimeter + water. $0.5 \times c \times 75 = (80 + 420) \times 10$. $37.5c = 5000$. $c = 133.3 \mathrm{Jkg}^{-1}\mathrm{K}^{-1}$. The answer key D is incorrect; the correct answer is B.
JAMB (UTME)
Physics
2000
Q7934.The diagram above shows a maximum and minimum thermometer divided into three portions P, Q and R. Which of the following is true about the respective contents of P, Q and R?
AAlcohol, mercury and alcohol
BAir, alcohol and mercury
CMercury, alcohol and mercury
DAir, mercury and alcohol.
Correct Answer: A
In a maximum-minimum thermometer, P and R contain alcohol and Q contains mercury.
JAMB (UTME)
Physics
2000
Q7935.The main reason for making the cover of a vacuum flask airtight is to prevent heat loss by
AConduction
BEvaporation
CRadiation
DConvection
Correct Answer: D
The airtight cover prevents convection currents.
JAMB (UTME)
Physics
2000
Q7936.A travelling wave moving from left to right has an amplitude of $0.15 \mathrm{m}$, a frequency of $550 \mathrm{Hz}$ and a wavelength of $0.01 \mathrm{m}$. The equation describing the wave is
Q7937.A transverse wave is applied to a string whose mass per unit length is $3 \times 10^{-2} \mathrm{kgm}^{-1}$. If the string is under a tension of $12 \mathrm{N}$, the speed of propagation of the wave is
Q7938.A quantity of water at $0^{\circ}\mathrm{C}$ is heated to about $30^{\circ}\mathrm{C}$. At each degree rise in temperature, its density will
ARise steadily
BRise then fall
CFall steadily
DFall then rise.
Correct Answer: B
Water has maximum density at $4^{\circ}\mathrm{C}$. It rises from $0$ to $4^{\circ}\mathrm{C}$ then falls.
JAMB (UTME)
Physics
2000
Q7939.A thin wire with heavy weights attached to both ends is hung over a block of ice resting on two supports. If the wire cuts through the ice block while the block remains solid behind the wire, the process is called
AFusion
BSublimation
CCondensation
DRegelation
Correct Answer: D
Regelation is the process where ice melts under pressure and refreezes when pressure is removed.
JAMB (UTME)
Physics
2000
Q7940.A cell of internal resistance $0.01 \Omega$ can be measured accurately using the
AOhm-meter
BPotentiometer
CElectroscope
DMetre bridge
Correct Answer: B
A potentiometer measures e.m.f. without drawing current, so it can measure internal resistance accurately.
JAMB (UTME)
Physics
2000
Q7941.An electron of charge $1.6 \times 10^{-19} \mathrm{C}$ and mass $9.1 \times 10^{-31} \mathrm{kg}$ is accelerated between two metal plates with a velocity of $4 \times 10^7 \mathrm{ms}^{-1}$. The potential difference between the plates is
Q7942.In the diagram above, a beam of white light travels from a rare to dense medium. What colours of light do the rays a, b, c respectively represent?
ABlue, yellow and red
BGreen, red and blue
CRed, green and blue
DBlue, green and red
Correct Answer: C
Red is deviated least and blue is deviated most.
JAMB (UTME)
Physics
2000
Q7943.The diagram above shows two capacitors P and Q of capacitances $5 \mu\mathrm{F}$ and $10 \mu\mathrm{F}$. Find the charges stored in P and Q respectively.
A$200 \mu\mathrm{C}$ and $100 \mu\mathrm{C}$
B$100 \mu\mathrm{C}$ and $200 \mu\mathrm{C}$
C$4 \mu\mathrm{C}$ and $2 \mu\mathrm{C}$
D$2 \mu\mathrm{C}$ and $4 \mu\mathrm{C}$
Correct Answer: B
In series, charge is the same. $Q = CV$. The total capacitance $= \dfrac{5 \times 10}{15} = 3.33 \mu\mathrm{F}$. $Q = 3.33 \times 20 = 66.7 \mu\mathrm{C}$. The answer key B is incorrect.
JAMB (UTME)
Physics
2000
Q7944.What optical instrument can best be constructed with converging lenses of focal lengths $500 \mathrm{cm}$ and $5 \mathrm{cm}$?
ACompound microscope
BTerrestrial telescope
CAstronomical telescope
DGalileo's telescope
Correct Answer: C
The large difference in focal lengths is suitable for an astronomical telescope.
JAMB (UTME)
Physics
2000
Q7945.If a charged ion goes through combined electric and magnetic fields, the resultant emergent velocity of the ion is
A$\dfrac{E}{B}$
B$\dfrac{B}{E}$
C$\dfrac{E}{B^2}$
D$E - B$
Correct Answer: A
For a velocity selector, $v = \dfrac{E}{B}$.
JAMB (UTME)
Physics
2000
Q7946.In the diagram above, the values of $V_1$ and $V_2$ are respectively
A$1 \mathrm{V}$ and $\dfrac{1}{3} \mathrm{V}$
B$\dfrac{1}{3} \mathrm{V}$ and $1 \mathrm{V}$
C$\dfrac{1}{3} \mathrm{V}$ and $2 \mathrm{V}$
D$1 \mathrm{V}$ and $\dfrac{2}{3} \mathrm{V}$
Correct Answer: B
Total resistance $= 3 + 2 + 1 = 6 \Omega$. $I = \dfrac{2}{6} = \dfrac{1}{3} \mathrm{A}$. $V_1 = \dfrac{1}{3} \times 3 = 1 \mathrm{V}$. $V_2 = \dfrac{1}{3} \times 2 = \dfrac{2}{3} \mathrm{V}$. The answer key B is incorrect; the correct answer is D.
JAMB (UTME)
Physics
2000
Q7947.A projector lantern is used to give the image of a slide on a screen. If the image is 24 times as large as the slide and the screen is $72.0 \mathrm{m}$ from the projecting lens, what is the position of the slide from the lens?
Q7948.A radio is operated by eight cells each of e.m.f. $2.0 \mathrm{V}$ connected in series. If two of the cells are wrongly connected, the net e.m.f. of the radio is
Q7949.A $2 \mathrm{H}$ inductor has negligible resistance and is connected to a $\dfrac{50}{\pi} \mathrm{Hz}$ a.c. supply. The reactance of the inductor is
Q7950.If the fraction of the atoms of a radioactive material left after 120 years is $\dfrac{1}{4}$, what is the half-life of the material?
A2 years
B10 years
C20 years
D24 years
Correct Answer: C
$\left(\dfrac{1}{2}\right)^n = \dfrac{1}{4} = \left(\dfrac{1}{2}\right)^2$. $n = 2$. $T_{1/2} = \dfrac{120}{2} = 60$ years. The answer key C is incorrect.