Two bulbs, one of $50\, watt$ and another of $25\, watt$ are connected in series to the mains. The ratio of the currents through them is
A$2:1$
B$1:2$
C$1:1$
D
Without voltage, cannot be calculated
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C$1:1$
c (c) The bulbs are in series, hence they will have the same current through them.
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In the circuit shown, the reading of the Ammeter is doubled after the switch is closed. Each resistor has a resistance $1\,\Omega$ and the ideal cell has an $e.m.f.$ $10\,V$. Then, the Ammeter has a coil resistance equal to ............ $\Omega$
At what temperature will the resistance of a copper wire become three times its value at $0\,^oC$ ................. $^oC$ (Temperature coefficient of resistance for copper = $4 × 10^{-3} \,per\, \,^oC$ )
Two rods of copper and iron with the same cross-sectional area are joined at $S$ and a steady current $I$ flows through the rods as shown in the figure. Choose the most appropriate representation of charges accumulated near the junction $S$.
The emf of a battery is $2\, V$ and its internal resistance is $0.5 \,\Omega$. The maximum power which it can deliver to any external circuit will be ............. $watt$
You are given a resistance wire of length $50\, cm$ and a battery of negligible resistance. In which of the following cases is largest amount of heat generated
First, a set of ${n}$ equal resistors of $10\; \Omega$ each are connected in series to a battery of emf $20\; {V}$ and internal resistance $10\; \Omega .$ A current $I$ is observed to flow. Then, the $n$ resistors are connected in parallel to the same battery. It is observed that the current is increased $20$ times, then the value of $n$ is .... .
It is preferable to measure the $e.m.f.$ of a cell by potentiometer than by a voltmeter because of the following possible reasons.
$(i)$ In case of potentiometer, no current flows through the cell.
$(ii)$ The length of the potentiometer allows greater precision.
$(iii)$ Measurement by the potentiometer is quicker.
$(iv)$ The sensitivity of the galvanometer, when using a potentiometer is not relevant.
Which of these reasons are correct?