Physics Test

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Physics Test - 32

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Weekly Quiz Competition

Question 1
5 / -1

The current gain of a transistor in a common emitter configuration is 50. If the emitter current is 5.5 mA, find the base current.

A
0.203 A

B
0.107 mA

C
0.107 A

D
0.203 mA

Solution

The expression for current gain is given as:

β = I₀/ I_B

I_C= 50I_B

Since, I_E= I_B+I_C

⇒ I_E= I_B+ 50I_B

I_E= 51I_B

I_B= IE51 = 5.551 = 0.107 mA
Question 2
5 / -1

A transistor having α = 0.90 is used in a common base amplifier. If the load resistance is 5.0 kΩ and the dynamic resistance of the emitter junction is 50 Ω, then calculate the voltage gain.

A
50

B
100

C
70

D
90

Solution

The expression of voltage gain is as follows:

A_V= αR_L / R_e

Given: α = 0.90, R_L = 5.0 kΩ = 5000 Ω, R_e = 50 Ω

A_V= 0.90 × 5000 / 50

A_V = 90
Question 3
5 / -1

What will the power gain of a transistor if it’s α value is 0.80 and the voltage gain is 95?

A
70

B
80

C
76

D
75

Solution

Power gain is defined as the ratio of output power to input power. It can also be determined as the product of current gain and voltage gain.

Given: α = 0.80, voltage gain (A_V) = 95

The required equation

⇒ A_P = α × A_V

A_P= 0.80×95

A_P= 76
Question 4
5 / -1

dentify the relationship between base current amplification (α) and emitter current amplification (β).

A
β = α / 1 - α

B
β = 1 - α / α

C
β = α / 1 + α

D
β = 1 + α / 1 - α

Solution

I_E= I_B+ I_C

I_E / I_C = I_B / I_C + 1

1α = 1 / β + 1

α = β / 1 + β

Therefore, β = α / 1−α
Question 5
5 / -1

A hydrogen atom in its ground state absorbs 10.2 eV of energy. What is the orbital angular momentum is increased by?

A
4.22 × 10^-3 Js

B
2.11 × 10^-34 Js

C
3.16 × 10^-34 Js

D
1.05 × 10^-34 Js

Solution

Increase in angular momentum = h /2π.

h /2π = 6.6 × 10⁻³⁴ /2 × 3.14

h /2π = 1.05 × 10^-34 Js.
Question 6
5 / -1

When a hydrogen atom is in its first excited level, what is the relation of radius and Bohr radius?

A
Twice

B
4 times

C
Same

D
Half

Solution

For the first excited level, n = 2.

r₂ = (2)²r₀ = 4r₀.

So, when a hydrogen atom is in its first excited level, its radius is 4 times of the Bohr radius.
Question 7
5 / -1

Which of the following is true regarding the Bohr model of atoms?

A
Assumes that the angular momentum of electrons is quantized

B
Uses Faraday’s laws

C
Predicts continuous emission spectra for atoms

D
Predicts the same emission spectra for all types of atoms

Solution

Bohr model of atoms assumes that the angular momentum of electrons is quantized. The atom is held between the nucleus and surroundings by electrostatic forces. The other options are not valid.
Question 8
5 / -1

What will be the longest wavelength in the Balmer series of hydrogen spectrum?

A
6557 × 10^-10 m

B
5557 × 10^-10 m

C
9557 × 10^-10 m

D
1557 × 10^-10 m

Solution
Question 9
5 / -1

The radius of the Bohr orbit depends on which of the following

A
1/n

B
n

C
n²

D
1/n²

Solution

The equation is given as:

From this, we can understand that r_n is directly proportional to n².
Question 10
5 / -1

Which theory is confirmed by the Davisson – Germer experiment?

A
de – Broglie theory

B
Newton’s theory

C
Einstein’s theory

D
Planck’s theory

Solution

Davisson and Germer experiment proves the concept of wave nature of matter particles. The Davisson–Germer experiment provides a critically important confirmation of the de-Broglie hypothesis, which said that particles, such as electrons, are of dual nature.

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Physics Test - 32

Result

Physics Test - 32

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SHARING IS CARING

Question 1

0.203 A

0.107 mA

0.107 A

0.203 mA

Solution

Question 2

50

100

70

90

Solution

Question 3

70

80

76

75

Solution

Question 4

β = α / 1 - α

β = 1 - α / α

β = α / 1 + α

β = 1 + α / 1 - α

Solution

Question 5

4.22 × 10-3 Js

2.11 × 10-34 Js

3.16 × 10-34 Js

1.05 × 10-34 Js

Solution

Question 6

Twice

4 times

Same

Half

Solution

Question 7

Assumes that the angular momentum of electrons is quantized

Uses Faraday’s laws

Predicts continuous emission spectra for atoms

Predicts the same emission spectra for all types of atoms

Solution

Question 8

6557 × 10-10 m

5557 × 10-10 m

9557 × 10-10 m

1557 × 10-10 m

Solution

Question 9

1/n

n

n2

1/n2

Solution

Question 10

de – Broglie theory

Newton’s theory

Einstein’s theory

Planck’s theory

Solution

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4.22 × 10^-3 Js

2.11 × 10^-34 Js

3.16 × 10^-34 Js

1.05 × 10^-34 Js

6557 × 10^-10 m

5557 × 10^-10 m

9557 × 10^-10 m

1557 × 10^-10 m

n²

1/n²