__PHYSICS JAMB 2021 GENERAL QUESTIONS AND ANSWERS__

Two cars moving in the same direction have speeds of 100 kmh^{-1} and 130 kmh^{-1} what is the velocity of the faster car as measured by an observer in the slower car?

**A.**30 kmh^{-1}**B.**130 kmh^{-1}**C.**200 kmh**D.**230 kmh^{-1}

A stone and a feather are dropped from the same height above the earth surface. ignoring air resistance, which of the following is correct?

**A.**the feather will be brown away by the wind while stone will drop steadily**B.**the stone and the feather will both reach the ground a the same time**C.**the feather will reach the ground first**D.**the stone will reach the ground first

A car moves with an initial velocity of 25 ms^{-1} and reaches a velocity of 45 ms^{-1} in 10s. what is the acceleration of the car?

**A.**2 ms^{-2}**B.**5 ms^{-2}**C.**20 ms^{-2}**D.**25 ms^{-2}

The surfaces of conveyor belts are made rough so as to

**A.**protect them while carrying loads**B.**prevent the loads from slipping**C.**enable them to carry more load**D.**make them stronger

A machine of velocity ratio 6 requires an effort of 400 N to raise a load of 800 N through I m. Find the efficiency of the machine

**A.**55. 6 %**B.**50.0%**C.**33.3%**D.**22.2%

In comparing the camera and the human eye, the film of the camera function as the

**A.**retina**B.**iris**C.**cornea**D.**pupil

An object 4 cm high is placed 15 cm from a concave mirror of focal length 5 cm. The size of the image is

**A.**2 cm**B.**3 cm**C.**4 cm**D.**5 cm

An object is embedded in a block of ice, 10 cm below the plane surface. if the refractive index of the ice is 1.50, the apparent depth below the surface is

**A.**2.50 cm**B.**6.67 cm**C.**7.50 cm**D.**7.63 cm

Which of the following is used for the correction of short sightedness?

**A.**convex lens**B.**concave lens**C.**convex mirror**D.**concave mirror

Dispersion occurs when white light passes through a glass prism because of the

**A.**different hidden colours in the glass**B.**different speeds of the colour in the glass**C.**defects in the glass**D.**high density of the glass

When a positively charged rod is brought nearer the cap of a positively charged electroscope, the leaves divergence will

**A.**be induced**B.**converge**C.**diverge**D.**remain constant

Power supply is transmitted at a very high voltage and low current in order to

**A.**make pass through the trasformers**B.**increase the power supply**C.**make it travel fast**D.**prevent overheating of the coil

A galvanometer with full-scale deflection of 10 mA is to be converted to a voltmeter with full-scale deflection of 5v. the resistance of the galvanometer is

**A.**1Ω**B.**2Ω**C.**5Ω**D.**10Ω

Two inductors of inductances 5 mll and 15 mll are connected in series and a current of 5A flows through them. the total energy stored in the inductor is

**A.**500.0J**B.**250.0J**C.**62.5J**D.**50.0J**E.**no correct option

In alternating current circuit at resonance, the angel of lead or lag is

**A.**π°**B.**(π)/2°**C.**(π)/3°**D.**0°

In a discharge tube, most of the gas is pumped out so that electricity is conducted at

**A.**low voltage**B.**steady voltage**C.**high pressure**D.**low pressure

The ground stated energy for the hydrogen atom is 5.44 x 10^{-19}J . If an electron drops from zero energy to ground state, calculate the frequency of the emitted radiation.

[h = 6.6 x 10^{-34} Js]

**A.**5.0 x 10^{16}Hz**B.**2.0 x 10^{16}Hz**C.**5.0 x 10^{15}Hz**D.**2.0 x 10^{15}Hz**E.**No correct option

Transistors are used for the

**A.**rectification of signals**B.**conversion of a.c to d.c**C.**amplification of signals**D.**conversion of d.c to a.c

Which of the following is a pure semiconductor?

**A.**carbon**B.**silicon**C.**transistor**D.**phosphorus

A bob of weight 0.1 N hangs from a massless string of length 50 cm. A variable horizontal force which increase from zero is applied to pull the bob until the string makes an angle of 60o with the vertical. The work done is

**A.**0.500 J**B.**0.250 J**C.**0.050 J**D.**0.025 J

Two metals P and Q of length l_{1} and l_{2} are heated through the same temperature difference. If the ratio of the linear expansivities of P to Q is 2:3 and the ratio of lengths is 3:4. What is the ratio of increase in length of P to Q?

**A.**7:5**B.**5:7**C.**1:2**D.**2:1

THe velocity of sound in air at 16^{o}C is 340ms^{-1}. What will it be when the pressure is doubled and its temperature raised to 127^{o}C?

**A.**400 ms^{-1}**B.**4,000 ms^{-1}**C.**8,000 ms^{-1}**D.**160,000 ms^{-1}

Three capacitors of capacitance 2μF, 4μFand 8μF are connected in parallel and a P.D of 6V is maintained across each capacitor, the total energy stored is

**A.**2.52 x 10^{-6}J**B.**6.90 x 10^{-6}J**C.**2.52 x 10^{-4}J**D.**6.90 x 10^{-4}J

A cell of e.m.f 12V and internal resistance 4Ω is connected to an external resistor of resistance 2Ω. Find the current flow.

**A.**5 A**B.**4 A**C.**3 A**D.**2 A

Three 4Ω resistors connected in parallel have a potential difference of 16 V applied across them. What is the total current in the circuit?

**A.**14 A**B.**12 A**C.**10 A**D.**8 A

In Faradays law of electrolysis, a graph of the mass deposited against the quantity of electricity is plotted. The slope of the graph gives

**A.**the energy released**B.**the electrochemical equivalent**C.**the current flowing**D.**the charge released

Rationalize 23√+5–√5–√−3–√23+55−3

**A.**3√15 – 11**B.**315√−112315−112**C.**3√15 + 11**D.**315√+112

Which of the following properties of a long steel bar would alter if the bar were melted, recast into a cube and allowed to cool to its original temperature?

**A.**sensity**B.**volume**C.**specific heat capacity**D.**electrical resistance

Which of the following instruments is best for measuring the diameter of a thin constantan wire?

**A.**callipers**B.**metre rule**C.**micometer screw guage**D.**vernier callipers

What is the density of a fuel of relative density 0.72? [Density of water = 1000kg m^{-3}]

**A.**72 kgm^{-3}**B.**720 kgm^{-3}**C.**7200 kgm^{-3}**D.**72000 kgm^{-3}