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

What will happen if two conducting spheres are separately charged and then brought in contact?

(a)

Total charge on the two spheres is conserved

(b)

The total energy is conserved

(c)

Both charge and energy are conserved

(d)

The final potential is the mean of the original potentials.

During charging a capacitor variation of potential V of the capacitor with time t as shown a

(a)

(b)

(c)

(d)

The total dipole moment per unit volume of the dielectric is________.

(a)

induction

(b)

charge distribution

(c)

polarisation

(d)

quantisation

The repulsive force between two like charges of 1 coulomb each separated by a distance of 1 m in vacuum is equal to :

(a)

9 x 10⁹ N

(b)

10⁹ N

(c)

9 x 10^-9 N

(d)

9 N

Near a charged object A another earthed object B is placed. Charges are induced on B. If B is removed. After that the charge on A ________.

(a)

remains the same

(b)

decreases

(c)

increases

(d)

becomes zero

In a large building, there are 15 bulbs of 40 W, 5 bulbs of 100 W, 5 fans of 80 W and 1 heater of 1 kW are connected. The voltage of electric mains is 220 V. The maximum capacity of the main fuse of the building will be ______.

(a)

14 A

(b)

8 A

(c)

10 A

(d)

12 A

An electron moves in a straight line inside a charged parallel plate capacitor of uniform charge density σ. The time taken by the electron to cross the parallel plate capacitor undeflected when the plates of the capacitor are kept under constant magnetic field of induction  \((\vec{B})\) is

(a)

\({ \varepsilon }_{ ° }\frac { elB }{ \sigma } \)

(b)

\({ \varepsilon }_{ ° }\frac { lB }{ \sigma {l} } \)

(c)

\({ \varepsilon }_{ ° }\frac { lB }{ {e}\sigma } \)

(d)

\({ \varepsilon }_{ ° }\frac { lB }{ \sigma } \)

Two short bar magnets have magnetic moments 1.20 Am² and 1.00 Am² respectively. They are kept on a horizontal table parallel to each other with their north poles pointing towards south. They have a common magnetic equator and are separated by a distance of 20.0 cm. The value of the resultant horizontal magnetic induction at the mid-point O of the line joining their centres is (Horizontal components of Earth’s magnetic induction is 3.6 × 10^–5 Wb m^–2 )

(a)

3.60 × 10^-5 Wb m^-2

(b)

3.5 × 10^-5 Wb m^-2

(c)

2.56 × 10^-4 Wb m^-2

(d)

2.2 × 10^-4 Wb m^-2

A thin semi-circular conducting ring (PQR) of radius r is falling with its plane vertical in a horizontal magnetic field B, as shown in the figure.

The potential difference developed across the ring when its speed v, is

(a)

Zero

(b)

\(\frac { { Bv\pi { r }^{ 2 } } }{ 2 } \) and P is at higher potential

(c)

πrBv and R is at higher potential

(d)

2rBv and R is at higher potential

In an electrical circuit, R, L, C, and AC voltage source are all connected in series. When L is removed from the circuit, the phase difference between the voltage and current in the circuit is \(\frac{\pi}{3}\). Instead, if C is removed from the circuit, the phase difference is again \(\frac{\pi}{3}\). The power factor of the circuit is

(a)

1/2

(b)

1/\(\sqrt2\)

(c)

1

(d)

\(\sqrt3\)/2

A power of 11,000 W is transmitted at 220 V. The current through line wires is _____________.

(a)

50 A

(b)

5 A

(c)

500 A

(d)

0.5 A

During the propagation of electromagnetic waves in a medium __________________.

(a)

electric energy density is double of the magnetic energy density

(b)

electric energy density is half of the magnetic energy density

(c)

electric energy density is equal to the magnetic energy density

(d)

both electric and magnetic energy densities are zero

Cellular phones use radio frequencies in ______________.

(a)

AM band

(b)

UHF band

(c)

FM band

(d)

upto 54 MHz

The absorption spectra are characteristic of the __________.

(a)

source

(b)

absorbing substance

(c)

time of travel from source to screen

(d)

spectrometer used to study the spectrum

A plane glass is placed over a various coloured letters (violet, green, yellow, red) The letter which appears to be raised more is _____.

(a)

red

(b)

yellow

(c)

green

(d)

violet

Two plane mirrors are parallel to each other and spaced 20cm apart. An object is kept in between them at 15cm from A. out of the following at which point on the image is not formed in mirror A (distance measured from mirror A) ___________.

(a)

15 cm

(b)

25 cm

(c)

45 cm

(d)

55 cm

A concave mirror of radius of curvature 60 cm is placed at the bottom and height of 20 cm, The mirror faces upwards with its axis vertical. Solar light fall normally on the surface of water and the image of the sun is formed. If a \(\\ \\ \\ { \mu }_{ \omega }=\cfrac { 4 }{ 3 } \)  then will the observer in air, the distance of the image from the surface of the water is ____________.

(a)

30 cm

(b)

10 cm

(c)

7.5 cm above

(d)

7.5 cm below

A light source of wavelength 520 nm emits 1.04 x 10¹⁵ photons per second while the second source of 460 nm produces 1.38 x 10¹⁵ photons per second. Then the ratio of power of second source to that of first source is _____.

(a)

1.00

(b)

1.02

(c)

1.5

(d)

0.98

The photo current in an experiment on photoelectric effect increases if ____________.

(a)

the intensity of the source is increased

(b)

the exposure time is increased

(c)

the intensity of the source is decreased

(d)

the exposure time is decreased

The clocks in moving ships will appear to go _______ clocks on earth.

(a)

faster than

(b)

slower than

(c)

the same as

(d)

stops after leaving earth

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

According to to Bohr, the relation between principal quantum number (n) and radius of the orbit (r) is _____________.

(a)

r α \(\frac1n\)

(b)

r α \(\frac{1}{n^2}\)

(c)

r α n

(d)

r α n²

A N-P-N transistor conducts when collector is _________ and emitter is ________ with respect to base.

(a)

positive, negative

(b)

positive, positive

(c)

negative, negative

(d)

negative, positive

The variation of frequency of carrier wave with respect to the amplitude of the modulating signal is called ______.

(a)

Amplitude modulation

(b)

Frequency modulation

(c)

Phase modulation

(d)

Pulse width modulation