1
COMEDK 2024 Morning Shift
+1
-0

A $$500 \mathrm{~W}$$ heating unit is designed to operate on a $$400 \mathrm{~V}$$ line. If line voltage drops to $$160 \mathrm{~V}$$, the percentage drop in heat output will be:

A
74%
B
85%
C
84%
D
75%
2
COMEDK 2024 Morning Shift
+1
-0

A cell of emf E and internal resistance r is connected to two external resistances $$\mathrm{R_1}$$ and $$\mathrm{R_2}$$ and a perfect ammeter. The current in the circuit is measured in four different situations:

(a) without any external resistance in the circuit.

(b) with resistance $$\mathrm{R_1}$$ only

(c) with $$\mathrm{R_1}$$ and $$\mathrm{R_2}$$ in series combination.

(d) with $$\mathrm{R_1}$$ and $$\mathrm{R_2}$$ in parallel combination.

The currents measured in the four cases in ascending order are

A
c < b < d < a
B
a < b < d < c
C
c < d < b < a
D
a < d < b < c
3
COMEDK 2024 Morning Shift
+1
-0

The current through a conductor is '$$\mathrm{a}$$' when the temperature is $$0^{\circ} \mathrm{C}$$. It is '$$\mathrm{b}$$' when the temperature is $$100^{\circ} \mathrm{C}$$. The current through the conductor at $$220^{\circ} \mathrm{C}$$ is

A
$$\frac{5 a b}{11 b-6 a}$$
B
$$\frac{5 a b}{6 a-11 b}$$
C
$$\frac{5 a b}{11 a-6 b}$$
D
$$\frac{11 a b}{5 a-6 b}$$
4
COMEDK 2024 Morning Shift
+1
-0

On increasing the temperature of a conductor, its resistance increases because

A
Electron density decreases
B
Relaxation time increases
C
Number of collisions between electrons decreases
D
Relaxation time decreases
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