1
JEE Advanced 2013 Paper 2 Offline
+3
-1

A thermal power plant produces electric power of 600 kW at 4000 V, which is to be transported to a place 20 km away from the power plant for consumers' usage. It can be transported either directly with a cable of large current carrying capacity or by using a combination of step-up and step-down transformers at the two ends. The drawback of the direct transmission is the large energy dissipation. In the method using transformers, the dissipation is much smaller. In this method, a step-up transformer is used at the plant side so that the current is reduced to a smaller value. At the consumers' end, a step-down transformer is used to supply power to the consumers at the specified lower voltage. It is reasonable to assume that the power cable is purely resistive and the transformers are ideal with power factor unity. All the currents and voltages mentioned are rms values.

If the direct transmission method with a cable of resistance 0.4 $$\Omega$$ km$$-$$1 is used, the power dissipation (in %) during transmission is

A
20
B
30
C
40
D
50
2
JEE Advanced 2013 Paper 2 Offline
+3
-1

A thermal power plant produces electric power of 600 kW at 4000 V, which is to be transported to a place 20 km away from the power plant for consumers' usage. It can be transported either directly with a cable of large current carrying capacity or by using a combination of step-up and step-down transformers at the two ends. The drawback of the direct transmission is the large energy dissipation. In the method using transformers, the dissipation is much smaller. In this method, a step-up transformer is used at the plant side so that the current is reduced to a smaller value. At the consumers' end, a step-down transformer is used to supply power to the consumers at the specified lower voltage. It is reasonable to assume that the power cable is purely resistive and the transformers are ideal with power factor unity. All the currents and voltages mentioned are rms values.

In the method using the transformers, assume that the ratio of the number of turns in the primary to that in the secondary in the step-up transformer is 1 : 10. If the power of the consumers has to be supplied at 200 V, the ratio of the number of turns in the primary to that in the secondary in the step-down transformer is

A
200 : 1
B
150 : 1
C
100 : 1
D
50 : 1
3
IIT-JEE 2012 Paper 2 Offline
+4
-1
In the given circuit, a charge of $$+80$$ $$\mu C$$ is given to the upper plate of the $$4$$ $$\mu F$$ capacitor. Then in the steady state, the charge on the upper plate of the $$3$$ $$\mu F$$ capacitor is
A
$$+ \,32\,\mu C$$
B
$$+ \,40\,\mu C$$
C
$$+ \,48\,\mu C$$
D
$$+ \,80\,\mu C$$
4
IIT-JEE 2012 Paper 1 Offline
+4
-1
Two large vertical and parallel metal plates having a separation of $$1$$ $$cm$$ are connected to a $$DC$$ voltage source of potential difference $$X$$. A proton is released at rest midway between the two plates. It is found to move at $${45^ \circ }$$ to the vertical JUST after release. Then $$X$$ is nearly
A
$$1 \times {10^{ - 5}}\,\,V$$
B
$$1 \times {10^{ - 7}}\,\,V$$
C
$$1 \times {10^{ - 9}}\,\,V$$
D
$$1 \times {10^{ - 10}}\,\,V$$
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