Physics Test 129

Result

Physics Test 129

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Weekly Quiz Competition

Question 1
4 / -1

A transformer has an efficiency of 80%. It is connected to a power input of 4 kW and 100 V. if the secondary voltage is 240 V, then the secondary current is

A
4.6 A

B
40 A

C
4.3 A

D
13.3 A

Solution
Question 2
4 / -1

Magnetic moments of two identical magnets are M and 2M respectively. Both are combined in such a way that their similar poles are same side. The time period in this case is ‘T₁’ .If polarity of one of the magnets is reversed its period becomes ‘T₂’ then find out ratio of their time periods T₁/T_2.

A
√3

B
1/√3

C
1

D
1/3

Solution
Question 3
4 / -1

The maximum current in a galvanometer can be 10 mA. It’s resistance is 10Ω. To convert it into an ammeter of 1 Amp. A resistor should be connected in

A
series, 0.1Ω

B
parallel, 0.1Ω

C
series, 100Ω

D
parallel, 100Ω.

Solution
Question 4
4 / -1

A soap bubble (surface tension = T) is charged to a maximum surface density of charge = σ, when it is just going to burst. Its radius R is given by:

A

B

C

D

Solution

Pressure due to surface tension

Pressure due to electrostatic force

Just before the bubble burst
Pressure due to surface tension = Pressure due to electrostatic force
Question 5
4 / -1

One mole of an ideal gas heated by law p = αV where P is pressure of gas, V is volume, α is a constant.
The heat capacity of gas in the process is-

A

B

C

D

Solution
Question 6
4 / -1

A sonometer wire resonates with a given tuning fork forming stationary waves with 5 antinodes, between 2 bridges, when a mass of 9 kg is suspended from the wire. When the mass is replaced by another mass m, the wire with the same tuning fork forms three antinodes, for the same position of the bridges. The value of m is

A
25 kg

B
22 kg

C
18 kg

D
12 kg

Solution

where μ is the mass per unit length of wire and T = weight of mass(Mg) and p is number of antinodes.
Since wire and the tuning fork are the same in both cases, so
Question 7
4 / -1

In a damped oscillator the amplitude of vibrations of mass m = 150 grams falls by 1/e times of its initial value in time t₀ due to viscous forces. The time t₀ and the percentage loss in mechanical energy during the above time interval t₀ respectively are (Let damping constant be 50 grams/s)

A

B

C

D

Solution
Question 8
4 / -1

A thermodynamic process of one mole ideal monoatomic gas is shown in figure. The efficiency of cyclic process ABCA will be :

A
25%

B
12.5%

C
50%

D

Solution
Question 9
4 / -1

An infinite current carrying wire, carrying current I is bent in V shape, lying in x-y plane as shown in figure. Intensity of magnetic field at point P will be (take OP = 2a)

A

B

C

D

Solution
Question 10
4 / -1

A silicon diode is connected in series with resistance and battery. What should be the value of battery if the reading of ammeter 3.62 A.

A
25.6

B
40.0

C
44.1

D
51.5

Solution

Rearranging the circuit,

As we know the potential drop across silicon diode in forward biased is 0.7V. Current flowing through the circuit is