2019 - JAMB Physics Past Questions and Answers - page 5
A siren having a ring of 200 hole makes 132 rev/min. A jet of air is directed on the set of holes. Calculate the frequency and wavelength in air of the note produced (take v = 350m/s)
0.875m
0.625m
0.335m
0.125m
n = 200, S = 132 rev/min, v = 350m/s\(^2\)
f = ns
| = | 200 | × | 132 | rev
min |
× | 1min
60s |
= | 440Hz |
| λ | = | v
f |
= | 350
440 |
= | 0.875m |
λ = 0.875m
A man on a bench will exert the greatest pressure on the bench when he
lies flat on his back
lies flat on his belly
stands on both feet
stands on the toes of one foot
P = F/A
Which shows that pressure is inversely proportional to areas, hence, pressure increases when the areas decrease and vice versa.
Gases conduct electricity under
high pressure & high voltage
low pressure & low voltage
normal pressure & low voltage
low pressure & high voltage
There is no perfect conductor or perfect insulator. In short, gases can conduct electricity, but they are considered insulators for the most part. Gas on its own cannnot conduct electricity but it can be made to conductor electricity by subjecting it under LOW PRESSURE and HIGH VOLTAGE.
Via https://physics.stackexchange.com/questions/38631/can-gases-conduct-electricity
Neutrons were discovered by
Faraday
Dalton
James Chadwick
Rutherford
The essential nature of the atomic nucleus was established with the discovery of the neutron by James Chadwick in 1932 and the determination that it was a new elementary particle, distinct from the proton.
The mass of a nucleus is the
total number of its proton & neutrons
number of its protons
mass of its electrons
total number of its protons & electrons
Three resistors with resistance 200Ω, 500Ω and 1kΩ are connected in series. A 6v battery is connected to either end of the combination. Calculate the potential difference between the ends of 200Ω resistance.
0.71V
0.7V
0.82V
0.8V
Req = 200 + 500 + 1000 = 1700Ω
| The potential difference, p.d | (across | 200Ω) | = | 200
1700 |
× | 6 | = | 0.71V |
pd = 0.71v
An a.c of 1A at a frequency of 800 cycles per second flows through a coil, the inductance of which is 2.5mH and the resistance of which is 5Ω. What is the power absorbed in the Coil?
5W
6W
7W
8W
I = 1A,
F = 800 cycles/s = 800Hz
R = 5Ω, L = 2.5mH
P = I\(^2\)R = I\(^2\) × 5 = 5W
P = 5W
In semi-conductor, the carriers of current at room temperature are
electrons only
electrons and holes
holes only
electron and ions
Electron and holes represents the negative and positive charges, respectively.
Water and Kerosine are drawn respectively into the two limbs of a Hare's apparatus. The destiny of water is 1.0gcm\(^{-3}\) and the density of kerosine is 0.80gcm\(^{-3}\). If the height of the water column is 20.0cm, calculate the height of the kerosine column.
1.6cm
16.0cm
20.0cm
25.0cm
for the different liquids,
d\(_1\)h\(_1\) = d\(_2\)h\(_2\)
1 × 20 = 0.8 × h
| h | = | 20
0.8 |
= | 25cm |
h = 25cm
When a girl moves towards a plane mirror at a speed of 4.0m/s, the distance between the girl & her image reduces a speed of
2 m/s
4 m/s
8 m/s
12 m/s
| v = | d
t |
or | v | α | d |
d = x, v = 4m/s
d = 2x, v = ? (girl & image)
| v | = | 2 × 4
x |
= | 8m/s |
v = 8m/s