Jamb 2019

Question 1

Blue and green color of light give

Answer 1

Cyan

Question 2

Electrons were Discovered by

Answer 2

JJ Thompson

Question 3

What are the limitations of Rutherford’s atomic model?

Answer 3

I. It is applicable when energy is radiated as electrons are revolving

II. It is applicable when energy is radiated in a continuous mode

Question 4

Ripple in a power supply unit is caused by

Answer 4

AC current

Question 5

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?

Answer 5

0*

Question 6

The pin-hole camera produces a less sharply defined image when the

Answer 6

Pin-hole is larger because of increased brightness

Question 7

Aluminium is sometimes used as the leaf of an electroscope because it

Answer 7

• Aluminum can be made in thin sheet like Gold.

- the leaf is a thin material that can be diverged easily.

Question 8

The conductivity of gases at low pressure can be termed as

Answer 8

Cold cathode emission or field emission

Question 9

Gas conduct electricity at

Answer 9

Low pressure and high voltage

Conduction takes places in gases when air is pumped out of a discharged tube under reduced pressure.

Question 10

The following are parts of the eye
I. Retina
II. Pupil
III. Iris
The correct equivalent in the camera in the same order are

Answer 10

• retina is similar to film
• pupil is similar to aperture
• iris is similar to diaphragm

Question 11

The momentum of a car moving at a constant speed in a circular track

Answer 11

can be zero depending on its position in the track

Question 12

The lead-acid accumulator consists of

Answer 12

• the positive pole is lead peroxide (PbO2)
• the negative pole is lead
• the electrolyte is H2SO4

Question 13

Green and red will give

Answer 13

Amber

Question 14

Red and blue will give

Answer 14

Magenta

Question 15

Frequency can be

Answer 15

n = # hole s = # of rev per sec

f = me

Question 16

Neutrons were discovered by

Answer 16

James Chadwick

Question 17

What is the reading accuracy of a meter rule?

Answer 17

M +_ 0.05cm

Question 18

Does Stable equilibrium brings about a increase or decrease in potential energy?

Answer 18

Stable equilibrium brings about increase in potential energy as the height rises after displacement.

Question 19

The lower the center of gravity

Answer 19

The more stable the object is

Question 20

The height at which the atmosphere ceases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is
(ρm = 13.6g/cm3
ρ = 0.00013g/cm3
)

A. 380mmHg
B. 570mmHg
C. 190mmHg
D. 480mmHg

Answer 20

13.6(760 - p) × 10−3
= 13 × 10−5
(20 × 103
)

760 - p = 13 × 10−5
× 20 × 103
13.6 × 10−3
= 19.12 × 101

760 - p = 191.2
p = 760 - 191.2 ≈ 570mmHg

Question 21

The equilibrium position of objects in any field corresponds to situation of

A. equipotential energy
B. maximum potential energy
C. minimum potential energy
D. minimum kinetic energy

Answer 21

Potential energy = mgh = (mg)h = force × distance

⇒ 0 × d = 0

Question 22

Sum of all forces acting on a body is zero.” This condition represents equilibrium’

A. First condition
B. Second condition
C. Third condition
D. Fourth condition

Answer 22

First condition

Question 23

A body moves in SHM between two point 20m on the straight line Joining the points. If the angular speed of the body is 5 rad/s. Calculate its speed when it is 6m from the center of the motion.

A. 20 m/s
B. 30 m/s
C. 40 m/s
D. 50 m/s

Answer 23

From two parts 20m apart
a = 10m, x = 6m, A = 5
V = ωA2−X2‾‾‾‾‾‾‾‾√
  = 5102−62‾‾‾‾‾‾‾‾√
 = 40m/s

Question 24

Efficiency of conduction in liquids and gases compared to solids is

A. less efficient than solid
B. more efficient than solids
C. equally efficient to solids
D. efficiently may vary

Answer 24

Less efficient than solids

Question 25

A safety precaution designed to prolong the life of a lead acid accumulator is A. By topping up the cells with concentrated acid B. The use of naked flame when charging the battery C. Keeping the specific gravity of the electrolyte within specified range D. By connecting wires to the terminals directly when testing the level of charging

Answer 25

- Topping is done with distilled water - Naked flame should be avoided when charging the battery - Direct connection of wires to the terminals should be avoided.

Question 26

The angular dispersion of a prism depends on

Answer 26

The refractive index only

Question 27

The length of the seconds hand of laboratory clock is 0.1m. Calculate the speed at the top of the seconds hand ``` A. 1.05 × 10−2 ms−1 B. 1.85 × 10−4 ms−1 C. 9.50 × 10−1 ms−1 D. 5.25 × 10−3 ms−1 View Answer & Discuss ```

Answer 27

A

Question 28

What is wavefront?

Answer 28

Wave front is a line or section taken through an advancing wave in which the particles are in phase.

Question 29

The lower fixed part of a faulty thermometer reads 2°C while the upper fixed point is 100°C. What is the true temperature when the thermometer reads 51°C? A. 52°C B. 50°C C. 49°C D. 46°C

Answer 29

50*C

Question 30

The Earth's magnetic equator passes through Jos in Nigeria. At Jos, the A. angle of variation is zero B. magnetic declination is 90 C. angle of dip is zero D. horizontal component at the Earth's field is zero

Answer 30

The angle of dip is at the equator

Question 31

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. A. 1.6cm B. 16.0cm C. 20.0cm D. 25.0cm

Answer 31

D

Question 32

When a girl moves towards a plane mirror at a speed of 4.0m/s, the distance between the girl & her image reduces at a speed of A. 2 m/s B. 4 m/s C. 8 m/s D. 12 m/s

Answer 32

C

Question 33

A microscope is focused on a mark on a table, when the mark is covered by a plate of glass 2m thick, the microscope has to be raised 0.67cm for the mark to be once more in focus. Calculate the refractive index. A. 1.50 B. 1.68 C. 2.58 D. 1.82

Answer 33

A