Electrostatics — Physics STD 12 Science — Question

Which of the following statements given below is not true in the context of magnetic lines of force?

In the diagram, three point charges (labeled 1, 2 and 3) are shown, along with the electric field around them. Which charge(s) is/ are positive?

Finger prints on a piece of paper may be detected by sprinkling fluorescent powder on the paper and then looking it into(a) Mercury light(b) Sunlight(c) Infrared light(d) Ultraviolet light

Comment on the statement given below:
In self-inductionWhen the current in a coil is increasing, induced emf opposes it
When the current in a coil is decreasing, induced emf supports it

In a transformer, the coefficient of mutual inductance between the primary and the secondary coil is 0.2 henry. When the current changes by 5 ampere/second in the primary, the induced e.m.f. in the secondary will be(a)  5 V    (b) 1 V(c)  25 V  (d) 10 V

A circular loop carrying a current is replaced by an equivalent magnetic dipole. A point on the axis of the loop is in:

Which is not true with respect to the cathode rays(a) A stream of electrons(b) Charged particles(c) Move with speed same as that of light(d) Can be deflected by magnetic fields

A point source of electromagnetic radiation has an average power output of 800 W. The maximum value of electric field at a distance 4.0 m from the source is(a) 64.7 V/m(b) 57.8 V/m(c) 56.72 V/m(d) 54.77 V/m

For measurement of potential difference, potentiometer is preferred in comparison to voltmeter because(a) Potentiometer is more sensitive than voltmeter(b) The resistance of potentiometer is less than voltmeter(c) Potentiometer is cheaper than voltmeter(d) Potentiometer does not take current from the circuit