JAMB Physics Past Questions & Answers - Page 421

2,101.

Flourescent tubes produces light by the

A.

excitation of gas molecules

B.

conduction of solar energy

C.

refraction of light by gas molecules

D.

thermal agitation of electron in the tubes

Correct answer is A

No explanation has been provided for this answer.

2,102.

The binding energy of helium 4He is
2

[atomic mass of proton = 1.00783U,
atomic mass of neutron = 1.00867U]

A.

4.033U

B.

2.017U

C.

0.033U

D.

0.330U

Correct answer is C

The binding energy of a nucleus, is the work done or energy needed to separate completely the nucleons (protons and neutrons) apart. Again, experiment shows that the total mass of all individual nucleons is greater than that of the nucleus, in which they are together. This difference in the mass is the measure of the binding energy of the particular nucleus.

For helium 4He,
2

it has altogether 4 nucleons 2 protons and 2 neutrons
2:H = 2 x 1.00783 = 2.01566
2:n = 2 x 1.00867 = 2.01734
∴ 2:H + 2:n = 4.03300u
But the helium nucleus has a mass of 4.00260u
∴ Binding energy = difference of nucleons and nucleus
= 4.03300U - 4.00260U = 0.03040U

2,103.

In a tuned radio receiver R, L, C series circuit for resonance, the inductive and capacitive reactance XL and XC respectively are related as

A.

XL = XC

B.

XL = 1/2XC

C.

XL = 1/XC

D.

XL = 2XC

Correct answer is A

In an R - L - C circuit resonance occurs when the inductive reactance (XL), is equal to the capacitive reactance (XC)
1.e XL = XC

2,104.

In a reverse biased junction diode, current flows in by

A.

positive holes alone

B.

majority carriers

C.

electron alone

D.

minority carriers

Correct answer is D

In a reverse biased junction diode only a very small current flows in, carried by the minority carriers which are the negative charges in the n-semi conductor

2,105.

The particle and wave nature of matter are demonstrated in the equation

A.

λ = hc/E

B.

λ = h/P

C.

λ = c/f

D.

λ = 2 d sin θ

Correct answer is B

I wave - particle duality of matter, the momentum of sub-atomic particle is given by P = h/λ where h = planck constant ; λ = wave length
=> λ = h/P