A car has a fresh battery of $e.m.f$. $12\, V$ and internal resistance of $0.05\, \Omega$. If the starter motor draws a current of $90\, A$, the terminal voltage when the starter is on will be ............... $V$
A$12$
B$10.5$
C$8.5$
D$7.5$
Medium
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D$7.5$
d $V = E - i.r = 12 - 90 \times 0.05 = 12 - 4.5 = 7.5\,V$.
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A heater is designed to operate with a power of $1000 \mathrm{~W}$ in a $100 \mathrm{~V}$ line. It is connected in combination with a resistance of $10 \Omega$ and a resistance $R$, to a $100 \mathrm{~V}$ mains as shown in figure. For the heater to operate at $62.5 \mathrm{~W}$, the value of $\mathrm{R}$ should be .................. $\Omega$.
Two heating coils, one of fine wire and the other of thick wire of the same material and of the same length are connected in series and in parallel. Which of the following statement is correct