Electric Charges and Fields — Physics STD 12 Science — Question

What is the value of electrical conductivity of a semiconductor at absolute zero?

A drop of mercury of radius 2mm is split into 8 identical droplets. Find the increase in surface energy. Surface tension of mercury = 0.465J/m².

Light from a point source falls on a screen. If the separation between the source and the screen is increased by 1%, the illuminance will decrease (nearly) by:

1. 0.5%
2. 1%
3. 2%
4. 4%

A rectangular brick is kept on a table with a part of its length projecting out. It remains at rest if the length projected is slightly less than half the total length but it falls down if the length projected is slightly more than half the total length. Give reason.

If plane of any loop is kept parallel to the magnetic field, then what is the magnitude of magnetic flux associated with the loop?

Current I flow through two parallel straight wires in the same direction/The wires are at a distance 2r from each other. What is the intensity of magnetic field atw the midpoint between the two wires?

Two wires of equal length are bent in the form of two loops. One of the loops is square shaped whereas the other loop is circular. These are suspended in a uniform magnetic field and the same current is passed through them. Which loop will experience greater torque? Give reasons.

Is a vector necessarily changed if it is rotated through an angle?

Name the part of electromagnetic spectrum which is used for taking photographs of earth under foggy conditions from great heights.