Four identical electrical lamps are labelled $1.5\,V$, $0.5\,A$ which describes the condition necessary for them to operate at normal brightness. A $12\,V$ battery of negligible internal resistance is connected to lamps as shown, then
Medium
Download our app for free and get started
For normal brightness of each bulb see following circuit. Current through each bulb $=$ $0.5\, A$
So main current $i = 2\,A$
Also, voltage across the combination $ = 1.5\,V$
So voltage across the resistance $ = 10.5\,V$
Hence for resistance $V = i\,R$ $ \Rightarrow $ $10.5 = 2 \times R$ $ \Rightarrow $ $R = \frac{{21}}{4}\,\Omega $
Download our appand get started for free
Experience the future of education. Simply download our apps or reach out to us for more information. Let's shape the future of learning together!No signup needed.*
Similar Questions
- 1In a potentiometer arrangement, a cell of $emf$ $1.25\,V$ gives a balance point at $35.0\,cm$ length of the wire. If the cell is replaced by another cell and the balance point shifts to $63.0\,cm,$ the $emf$ of the second cell ............... $V$View Solution
- 2The charge supplied by source varies with time $'t'$ as $Q = at -bt^2$. The total heat produced in the resistor $2R$ before current reduces to zeroView Solution
- 3In the given circuit ' $a$ ' is an arbitrary constant. The value of $m$ for which the equivalent circuit resistance is minimum, will be $\sqrt{\frac{ x }{2}}$. The value of $x$ is ...........View Solution
- 4View SolutionThe material of fuse wire should have
- 5A hollow cylindrical conductor has length of $3.14\,m$, while its inner and outer diameters are $4\,mm$ and $8\,mm$ respectively. The resistance of the conductor is $n \times 10^{-3}\,\Omega$.If the resistivity of the material is $2.4 \times 10^{-8}\,\Omega\,m$. The value of $n$ is $..........$View Solution
- 6View SolutionIn a metallic conductor, under the effect of applied electric field, the free electrons of the conductor
- 7A voltmeter of resistance $1000\,\Omega$ is connected across a resistance of $500\, \Omega$ in the given circuit. What will be the reading of voltmeter .............. $V$View Solution
- 8If a copper wire is stretched to increase its length by $20 \% $. The percentage increase in resistance of the wire is $..........\%$View Solution
- 9View SolutionWhich of the following statements is false?
- 10If $X, Y$ and $Z$ in figure are identical lamps, which of the following changes to the brightnesses of the lamps occur when switch $S$ is closed?View Solution
