2022 - JAMB Physics Past Questions and Answers - page 2
Which of the following liquid is a poor conductor of electricity?
Distilled water
Tap water
Sea water
Drinking water
Distilled water is free from electrolytes; it does not contain any salts, minerals or acids and hence doesn't have any conducting substance in it. In other words, it is a poor conductor of electricity.
An isotope has an initial activity of 120 Bq. 6 days later its activity is 15 Bq. What is half-life?
3 days
2 days
1 day
4 days
the amount left undecayed = A
the initial amount = A0
the number of half-lives that passed in a period of time = t:
\(\frac{1}{2^n} * A_0 = A\)
\(\frac{1}{2^n} * 120 = 15\)
\(\frac{1}{2^n}\) = \(\frac{15}{120}\)
\(\frac{1}{2^n}\) = \(\frac{1}{8}\)
\(\frac{1}{2^n}\) = \(\frac{1}{2^3}\)
\(2^n = 2^3\)
n = 3
6days/3 = 2 days
In order to remove the error of parallax when taking measurements with a metre rule, the eye should be focused___
slantingly towards the right on the markings
slantingly towards the left on the markings
vertically downwards on the markings
vertically upwards on the markings
An athlete standing waist-deep in a swimming pool appears to have short legs because of the light__?
diffraction
refraction
reflection
interference
Because the refractive index of water is greater than that of air the athlete's legs appear to be short while standing in the pool due to refraction.
A tuning fork that has a frequency of 312Hz emits a wave which has a wavelength of 1.10 m. Find the velocity of sound.
312.0 ms\(^{-1}\)
110.0 ms\(^{-1}\)
343.2 ms\(^{-1}\)
686.4 ms\(^{-1}\)
When the plate surface area of a capacitor increases, ___?
the voltage can withstand increase
the capacitance decreases
the capacitance is unaffected
the capacitance increases
As the surface area of the plates increases, capacitance increases because larger plates provide greater capacity to store electric charge.
An electromagnetic relay is a device used for?
reading the magnitude of magnetic flux
controlling another circuit carrying larger current
turning in sports
storing magnetic field
An electromagnetic relay is an electrically operated switch that uses a magnet to turn the switch on or off.
According to kinetic molecular model in gases,
the particles are closely packed together; they occupy minimum space are usually arranged in a regular pattern
the particles vibrate about fixed positions and are held together by the strong intermolecular bonds between them
the molecules are very far apart and occupy all the spaces made available to them
the particles occur in clusters with molecules slightly further apart
According to the kinetic molecular model in gases, gas particles are in constant motion and exhibit perfectly elastic collisions.
The main postulates of the theory are:
(1) the particles in a gas are in constant, random motion
2) the combined volume of the particles is negligible
(3) the particles exert no forces on one another
(4) any collisions between the particles are completely elastic
(5) the average kinetic energy of the particles is proportional to the temperature in kelvins
A current of 0.5 A flows through a resistor when connected to a 40 V battery. How much energy is dispatched in 2 minutes?
2400 J
9600 J
1500 J
1200 J
Energy = power x time
Power = voltage x current.
Energy = voltage x current x time
Energy = 40 x 0.5 x 60 x 2
= 2,400j
For a pear-shaped conductor shown, the concentration of charge on the outside is highest at?
X
Z
Y
K
Electrons tend to concentrate on the location with more curvature, that is, sharp edges.