A coil develops heat of $800\, cal/sec$. When $20\, volts$ is applied across its ends. The resistance of the coil is .............. $\Omega$ ($1$ $cal$ = $4.2$ $joule$)
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Two resistance of $100\ \Omega$ and $200\ \Omega$ are connected in series with a battery of $4 \mathrm{~V}$ and negligible internal resistance. $A$ voltmeter is used to measure voltage across $100 \Omega$ resistance, which gives reading as $1 \mathrm{~V}$. The resistance of voltmeter must be ___$\Omega$.
Current $l$ versus time $t$ graph through a conductor is shown in the figure. Average current through the conductor in the interval $0$ to $15 \,s$ is ............ $A$
Two square metal plates $A$ and $B$ are of the same thickness and material. The side of $B$ is twice that of $A$. These are connected as shown in series. If the resistances of $A$ and $B$ are denoted by $R_A$ and $R_B,$ then $(R_A/R_B)$ is
In a meter bridge experiment, resistances are connected as shown in the following figure. The balancing length $l_1$ is $55\, cm$. Now, an unknown resistance $x$ is connected in series with $P$ and the new balancing length is found to be $75\, cm$. The value of $x$ is
During an experiment with a metre bridge, the galvanometer shows a null point when the joceky is pressed at $40.0 \ cm$ using a standard resistance of $90 \ \Omega$, as shown in the figure. The least count of the scale used in the meter bridge is $1 \ mm$. The unknown resistance is: