A $220\, volt$ and $800\, watt$ electric kettle and three $220\, volt$ and $100\, watt$ bulbs are connected in parallel. On connecting this combination with $220\, volt$ electric supply, the total current will be ................ $ampere$
A$0.15$
B$5.0$
C$5.5$
D$6.9$
Medium
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B$5.0$
b (b) Total power $P = (800 + 3 \times 100)$
Also $P = Vi$ $ \Rightarrow $ $1100 = 220 \times i$ $ \Rightarrow $ $i = 5\,A$
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$A$ brass disc and a carbon disc of same radius are assembled alternatively to make a cylindrical conductor. The resistance of the cylinder is independent of the temperature. The ratio of thickness of the brass disc to that of the carbon disc is [$\alpha$ is temperature coefficient of resistance and Neglect linear expansion ]
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?
Four wires $AB,\,\,BC,\,\,CD,\,\,DA$ of resistance $4\, \Omega$ each and a fifth wire $BD$ of resistance $8\, \Omega$ are joined to form a rectangle $ABCD$ of which $BD$ is a diagonal. The effective resistance between the points $A$ and $B$ is
The resistance of a wire is $R$. It is bent at the middle by $180^{\circ}$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is