1
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

Two radioactive materials X$$_1$$ and X$$_2$$ have decay constant 5$$\lambda$$ and $$\lambda$$, respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of X$$_1$$ to X$$_2$$ will be $$1/e$$ after a time

A
$$1/4\lambda$$
B
$$e/\lambda$$
C
$$\lambda$$
D
$$\frac{1}{2}\lambda$$
2
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

The Poisson's ratio of a material is 0.1. If the longitudinal strain of a rod of this material is $$10^{-3}$$, then the percentage change in the volume of the rod will be

A
0.008%
B
0.08%
C
0.8%
D
8%
3
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

A satellite can be in a geostationary orbit around a planet if it is at a distance R from the centre of the planet. If the planet starts rotating about its axis with double the angular velocity, then to make the satellite geostationary, its orbital radius should be

A
$$2R$$
B
$$\frac{R}{2}$$
C
$$\frac{R}{2^{1/3}}$$
D
$$\frac{R}{4^{1/3}}$$
4
COMEDK 2020
MCQ (Single Correct Answer)
+1
-0

When a $$p$$-$$n$$ junction diode is connected in forward bias, its barrier potential

A
decreases and less current flows in the circuit
B
decreases and more current flows in the circuit
C
increases and more current flows in the circuit
D
decreases and no current flows in the circuit
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