Science (English Medium) Class 12 - CBSE Question Bank Solutions for Physics

Which of the following is responsible for the earth’s magnetic field?

Which of the following independent quantities is not used to specify the earth’s magnetic field?

The angle of dip at a certain place where the horizontal and vertical components of the earth’s magnetic field are equal is ______.

The vertical component of earth’s magnetic field at a place is √3 times the horizontal component the value of angle of dip at this place is ______.

At a given place on earth’s surface the horizontal component of earth’s magnetic field is 2 × 10^3-5 T and resultant magnetic field is 4 × 10^3-5 T. The angle of dip at this place is ______.

The net magnetic flux through any closed surface, kept in a magnetic field is ______.

The natural frequency (ca₀) of oscillations in LC circuit is given by ______.

A transformer works on the principle of ______.

For an ideal step-down transformer, the quantity which is constant for both the coils is ______.

An electric dipole of moment p is placed parallel to the uniform electric field. The amount of work done in rotating the dipole by 90° is ____________.

The horizontal component of earth’s magnetic field at a place is `sqrt3` times the vertical component. The angle of dip at that place is ______.

The small angle between magnetic axis and geographic axis at a place is ______.

Which among the following, is not a cause for power loss in a transformer?

Assertion(A): A magnetic needle free to rotate in a vertical plane, orients itself (with its axis) vertical at the poles of the earth.

Reason (R): At the poles of the earth the horizontal component of earth’s magnetic field will be zero.

Select the most appropriate answer from the options given below:

Read the following paragraph and answer the question:

Long distance power transmissions

The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.

Which of the following statement is true?

Read the following paragraph and answer the question:

Long distance power transmissions

The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.

If the secondary coil has a greater number of turns than the primary, ______.

Read the following paragraph and answer the question:

Long distance power transmissions

The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.

We need to step-up the voltage for power transmission, so that ______.

Read the following paragraph and answer the question:

Long distance power transmissions

The large-scale transmission and distribution of electrical energy over long distances is done with the use of transformers. The voltage output of the generator is stepped up. It is then transmitted over long distances to an area sub-station near the consumers. There the voltage is stepped down. It is further stepped down at distributing sub-stations and utility poles before a power supply of 240 V reaches our homes.

A power transmission line feeds input power at 2300 V to a step down transformer with its primary windings having 4000 turns. The number of turns in the secondary in order to get output power at 230 V are ______.

A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different numbers of turns and wound on the same soft iron core.

The number of turns in the primary and secondary coils of an ideal transformer is 2000 and 50 respectively. The primary coil is connected to a main supply of 120 V and secondary coil is connected to a bulb of resistance 0.6 Ω.

The value of voltage across the secondary coil is ______.

A transformer is essentially an a.c. device. It cannot work on d.c. It changes alternating voltages or currents. It does not affect the frequency of a.c. It is based on the phenomenon of mutual induction. A transformer essentially consists of two coils of insulated copper wire having different numbers of turns and wound on the same soft iron core.

The number of turns in the primary and secondary coils of an ideal transformer is 2000 and 50 respectively. The primary coil is connected to a main supply of 120 V and secondary coil is connected to a bulb of resistance 0.6 Ω.

The value of current in the bulb is ______.