1
JEE Main 2016 (Online) 10th April Morning Slot
+4
-1
The resistance of an electrical toaster has a temperature dependence given by R(T) = R0 [1 + $$\alpha$$(T − T0)] in its range of operation. At T0 = 300 K, R = 100 $$\Omega$$ and at T = 500 K, R = 120 $$\Omega$$. The toaster is connected to a voltage source at 200 V and its temperature is raised at a constant rate from 300 to 500 K in 30 s. The total work done in raising the temperature is :
A
400 $$\ln \,{{1.5} \over {1.3}}\,J$$
B
200 $$\ln \,{{2} \over {3}}\,J$$
C
60000 $$\ln \,{{6} \over {5}}\,J$$
D
300 J
2
JEE Main 2016 (Online) 9th April Morning Slot
+4
-1

In the circuit shown, the resistance r is a variable resistance. If for r = fR, the heat generation in r is maximum then the value of f is :
A
$${1 \over 4}$$
B
$${1 \over 2}$$
C
$${3 \over 4}$$
D
1
3
JEE Main 2016 (Offline)
+4
-1
The temperature dependence of resistance of $$Cu$$ and undoped $$Si$$ in the temperature range $$300-400$$ $$K,$$ is best described by :
A
Linear increases for $$Cu,$$ exponential decrease of $$Si.$$
B
Linear decrease for $$Cu,$$ linear decrease for $$Si$$
C
Linear increase for $$Cu,$$ linear increase for $$Si.$$
D
Linear increase for $$Cu,$$ exponential increase for $$Si$$
4
JEE Main 2015 (Offline)
+4
-1
When $$5V$$ potential difference is applied across a wire of length $$0.1$$ $$m,$$ the drift speed of electrons is $$2.5 \times {10^{ - 4}}\,\,m{s^{ - 1}}.$$ If the electron density in the wire is $$8 \times {10^{28}}\,\,{m^{ - 3}},$$ the resistivity of the material is close to :
A
$$1.6 \times {10^{ - 6}}\Omega m$$
B
$$1.6 \times {10^{ - 5}}\Omega m$$
C
$$1.6 \times {10^{ - 8}}\Omega m$$
D
$$1.6 \times {10^{ - 7}}\Omega m$$
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