#### 12th Standard Physics English Medium Free Online Test Book Back one Mark questions - Part Two

12th Standard

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Physics

Time : 00:10:00 Hrs
Total Marks : 10
Answer all the questions
10 x 1 = 10
1. Three capacitors are connected in triangle as shown in the figure. The equivalent capacitance between the points A and C is

(a)

1μF

(b)

2μF

(c)

3μF

(d)

$\frac{1}{4}$μF

2. A piece of copper and another of germanium are cooled from room temperature to 80 K. The resistance of

(a)

each of them increases

(b)

each of them decreases

(c)

copper increases and germanium decreases

(d)

copper decreases and germanium increases

3. A flat dielectric disc of radius R carries an excess charge on its surface. The surface charge density is σ. The disc rotates about an axis perpendicular to its plane passing through the center with angular velocity ω. Find the magnitude of the torque on the disc if it is placed in a uniform magnetic field whose strength is B which is directed perpendicular to the axis of rotation

(a)

$\frac { 1 }{ 4 } \sigma \omega \pi BR$

(b)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 2 }$

(c)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 3 }$

(d)

$\frac { 1 }{ 4 } \sigma \omega \pi B{ R }^{ 4 }$

4. In an oscillating LC circuit, the maximum charge on the capacitor is Q. The charge on the capacitor when the energy is stored equally between the electric and magnetic fields is

(a)

$\frac{Q}{2}$

(b)

$\frac{Q}{\sqrt3}$

(c)

$\frac{Q}{\sqrt2}$

(d)

Q

5. Which of the following is NOT true for electromagnetic waves?

(a)

it transport energy

(b)

it transport momentum

(c)

it transport angular momentum

(d)

in vacuum, it travels with different speeds which depend on their frequency

6. Light transmitted by Nicol prism is,

(a)

partially polarised

(b)

unpolarised

(c)

plane polarised

(d)

elliptically polarised

7. The work functions for metals A, B and C are 1.92 eV, 2.0 eV and 5.0 eV respectively. The metals which will emit photoelectrons for a radiation of wavelength 4100$\\ \\ \mathring { A } \\$ is/are

(a)

A only

(b)

both A and B

(c)

all these metals

(d)

none

8. The half-life period of a radioactive element A is same as the mean life time of another radioactive element B. Initially both have the same number of atoms. Then

(a)

A and B have the same decay rate initially

(b)

A and B decay at the same rate always

(c)

B will decay at faster rate than A

(d)

A will decay at faster rate than B.

9. The frequency range of 3 MHz to 30 MHz is used for

(a)

Ground wave propagation

(b)

Space wave propagation

(c)

Sky wave propagation

(d)

Satellite communication

10. The technology used for stopping the brain from processing pain is

(a)

Precision medicine

(b)

Wireless brain sensor

(c)

Virtual reality

(d)