2019 - JAMB Physics Past Questions and Answers - page 2
Electrons were discovered by
Dalton
James Charwick
J.J. Thompson
Niels Bohr
Which of the following is/are the limitations to the Rutherford's atomic models?
I. It is applicable when energy is radiated as electrons are revolving
II. It is applicable when energy is radiated in a continuous mode
III. It is applicable to an atom with only one electron in the other shell
I only
II only
I & II only
I, II & III only
Rutherford's model assumed the following which forms limitations of the model:
- energy is radiated when electrons are revolving
- energy is radiated in a continuous mode
Which of the following equations is the correct definition of the reactance of an indicator L?
Reactance = (Amplitude of voltage) \(\div\) (Amplitude of current)
Reactance = (Amplitude of voltage) x (Amplitude of current)
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)
Reactance = (Amplitude of current)\(^2\) \(\div\) (Amplitude of voltage)\(\frac{1}{2}\)
Reactance is a form of opposition that electronic components exhibit to the passage of alternating current (alternating current) because of capacitance or inductance.
Resistance and reactance combine to form impedance
Ripple in a power supply unit is caused by
using an alternating current source
forward voltage drop
heavy load
using a zener diode
The fluctuation of d.c signal results from the rectification of AC to DC
When the temperature of a liquid is increased, its surface tension
increases
decreases
remain constant
increases then decreases
In general, surface tension decreases when the temperature increases because cohesive forces decrease with an increase of molecular thermal activity. The influence of the surrounding environment is due to the adhesive action of liquid molecules that they have at the interface.
The distance between an object and its real image in a convex lens is 40cm. If the magnification of the image is 3, calculate the focal length of the lens
6.5 cm
7.5 cm
8.5 cm
4.5 cm
Formula:
u + v = 40
\(\frac{v}{u}\) = 3
v = 3u
u + 3u = 40
4u = 40
u = 10cm
v = 3u = 30cm
f = \(\frac{uv}{u + v} = \frac{10(30)}{10 + 30} = \frac{300}{40}\)
f = 7.5 cm
A ray of light passes through the centre of curvature of a concave mirror and strikes the mirror. At what angle is the ray reflected?
180\(^o\)
90\(^o\)
0\(^o\)
60\(^o\)
When a ray of light passes through the centre of curvature, it is returned along the same path with the angle difference along the same path equal to zero
The pin-hole camera produces a less sharply defined image when the
pin-hole is larger
illumination is less
screen is further from the pin-hole
object is further from the pin-hole
Increased brightness leads to a less sharp or blurred image. Also, increase brightness is consequent upon a large hole or multiple pinholes
A straight wire 15cm long, carrying a current of 6.0A is in a uniform field of 0.40T. What is the force on the wire when it is at right angle to the field
0.46N
0.35N
0.36N
0,24N
The pitch of a screw jack is 0.45cm and the arm is 60cm long. If the efficiency of the Jack is 75/π %, calculate the mechanical advantage.
400
300
200
150
P = 0.45cm,
L = 60cm,
Efficiency(eff) = 75/π%
| VR Screw system = | 2πr
P |
= | 2πL
P |
| M.A | = | Eff% × VR
100 |
= | 75
π |
× | 1
100 |
× | 2π × 60
0.45 |
= | 75 × 800
300 |
= | 200 |
Hence, M.A = 200