Electromagnetic Waves — Physics STD 12 Science — Question

From the graph between current I and voltage V shown below, identify the portion corresponding to negative resistance

(a) AB

(b) BC

(c) CD

(d) DE

The desirable properties for making permanent magnets are:

1. High retentivity and high coercive force.
2. High retentivity and low coercive force.
3. Low retentivity and high coercive force.
4. Low retentivity and low coercive force.

What is the resistance of a carbon resistance which has bands of colours brown, black and brown

(a) 100 W

(b) 1000 W

(c) 10 W

(d) 1 W

The force that a unit positive charge would experiences if placed at that point is called as _____ due to charge at a point in space.

The molecules in which centres of positive and negative charges coincide are called as:

The decay constant λ  of the radioactive sample is the probability of decay of an atom in unit time, then

(a) λ decreases as atoms become older

(b) λ increases as the age of atoms increases

(c) λ is independent of the age

(d) Behaviour of λ with time depends on the nature of the activity

An electron moving with a uniform velocity along the positive x-direction enters a magnetic field directed along the positive y-direction. The force on the electron is directed along

(a) Positive y-direction	(b) Negative y-direction
(c) Positive z-direction	(d) Negative z-direction

An inductor, L a resistance R and two identical bulbs, and    are connected to a battery through a switch S as shown in the figure. The resistance R is the same as that of the coil that makes L. Which of the following statements gives the correct description of the happenings when the switch S is closed

(a) The bulb B2 lights up earlier than B1 and finally both the bulbs shine equally bright

(b) B1 light up earlier and finally both the bulbs acquire equal brightness

(c) B2 lights up earlier and finally B1 shines brighter than B2

(d) B1 and B2 light up together with equal brightness all the time

10 gm of radioactive material of half-life 15 year is kept in store for 20 years. The disintegrated material is

(a) 12.5 g

(b) 10.5 g

(c) 6.03 g

(d) 4.03 g

Image of any object formed at the retina of human eye is :