1
JEE Main 2024 (Online) 31st January Evening Shift
+4
-1

By what percentage will the illumination of the lamp decrease if the current drops by 20%?

A
26%
B
36%
C
46%
D
56%
2
JEE Main 2024 (Online) 31st January Evening Shift
+4
-1

The resistance per centimeter of a meter bridge wire is $$r$$, with $$X \Omega$$ resistance in left gap. Balancing length from left end is at $$40 \mathrm{~cm}$$ with $$25 \Omega$$ resistance in right gap. Now the wire is replaced by another wire of $$2 r$$ resistance per centimeter. The new balancing length for same settings will be at

A
10 cm
B
80 cm
C
40 cm
D
20 cm
3
JEE Main 2024 (Online) 31st January Morning Shift
+4
-1

Two conductors have the same resistances at $$0^{\circ} \mathrm{C}$$ but their temperature coefficients of resistance are $$\alpha_1$$ and $$\alpha_2$$. The respective temperature coefficients for their series and parallel combinations are :

A
$$\alpha_1+\alpha_2, \frac{\alpha_1 \alpha_2}{\alpha_1+\alpha_2}$$
B
$$\frac{\alpha_1+\alpha_2}{2}, \frac{\alpha_1+\alpha_2}{2}$$
C
$$\alpha_1+\alpha_2, \frac{\alpha_1+\alpha_2}{2}$$
D
$$\frac{\alpha_1+\alpha_2}{2}, \alpha_1+\alpha_2$$
4
JEE Main 2024 (Online) 30th January Evening Shift
+4
-1

When a potential difference $$V$$ is applied across a wire of resistance $$R$$, it dissipates energy at a rate $$W$$. If the wire is cut into two halves and these halves are connected mutually parallel across the same supply, the energy dissipation rate will become:

A
1/2W
B
4W
C
1/4W
D
2W
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