2004 - JAMB Physics Past Questions and Answers - page 5
41
A moving coil galvanometer has a full-scale deflection of 3A equivalent to 30o deflection. The sensitivity of the instrument is
A
33.0
B
0.1
C
90.0
D
10.0
correct option: d
Sensitivity of a measuring instrument is given by deflection per unit current: and given that deflection = 30o; and current (I) = 3A: then the sensitivity of the meter = 30/0 = 10.0
Users' Answers & Comments42
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 option: 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
Users' Answers & Comments=> λ = h/P
43
In a reverse biased junction diode, current flows in by
A
positive holes alone
B
majority carriers
C
electron alone
D
minority carriers
correct option: 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
Users' Answers & Comments44
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 option: 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
Users' Answers & Comments1.e XL = XC
45
| The binding energy of helium | 4 | He 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 option: 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.
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
Users' Answers & Comments| For helium | 4 | He, |
| 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
46
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 option: a
Users' Answers & Comments47
The energy stored in an inductor of inductance 5mH when a current of 6A flows through it is
A
9.0 x 10-3J
B
9.0 x 10-2J
C
1.4 x 10-2J
D
1.8 x 10-3J
correct option: b
Energy stored in a coil of inductance, L, and carry a current, I is given by
E = 1/2 L I2
= 1/2 x 5 x 10-3 x 6 x 6
= 9.0 x 10-2J
Users' Answers & CommentsE = 1/2 L I2
= 1/2 x 5 x 10-3 x 6 x 6
= 9.0 x 10-2J
48
Which of the following is an electrolyte?
A
Paraffin
B
Sugar solution
C
Grape fruit
D
Alcohol
correct option: c
Users' Answers & Comments49
A steady current of 2A flows in a coil of emf 12V for 0.4s. A back emf of 3V was induced during this period. The stored energy in the loop that can be utilized is
A
9.6J
B
2.4J
C
12.0J
D
7.2J
correct option: b
Energy stored = Ivt = current x back e.m.f x time
= 2 x 3 x 0.4
= 2.4J
Users' Answers & Comments= 2 x 3 x 0.4
= 2.4J
50
The instrument used for securing a large number of similar charges by induction is called
A
electrophorus
B
capacitor
C
proof-plane
D
electroscope
correct option: a
Users' Answers & Comments