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(b) (i) How many bulbs of resistance $8\ \Omega$ each should be connected in parallel combination to draw a current of $2\ \text{A}$ from a battery of $4\ \text{V}$?
(ii) Name the device used for measuring electric current. How is it connected in a circuit ?
(iii) State Joule's law of heating.
(ii) Name the device used for measuring electric current. How is it connected in a circuit ?
(iii) State Joule's law of heating.
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(b)
(i) $V=4\text{V}, I= 2\text{A}$
Resistance of circuit $R = \frac{V}{I}$
$R=\frac{4}{2}$
$R = 2\Omega$ (½)
Let 'n' be the number of bulbs
$\frac{1}{R} = \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + ---n$
$\frac{1}{R} = \frac{n}{8}$
$\frac{1}{2} = \frac{n}{8}$
$n=4$
Therefore, 4 bulbs of resistance $8 \Omega$ should be connected in parallel. (1)
(ii)
• Ammeter (1)
• In series (1)
(iii) Heat generated through a current carrying conductor is directly
proportional to square of current, resistance of conductor and time
for which current flows in conductor. (1)
/
$H=I^2Rt$ (1)
(i) $V=4\text{V}, I= 2\text{A}$
Resistance of circuit $R = \frac{V}{I}$
$R=\frac{4}{2}$
$R = 2\Omega$ (½)
Let 'n' be the number of bulbs
$\frac{1}{R} = \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + \frac{1}{8} + ---n$
$\frac{1}{R} = \frac{n}{8}$
$\frac{1}{2} = \frac{n}{8}$
$n=4$
Therefore, 4 bulbs of resistance $8 \Omega$ should be connected in parallel. (1)
(ii)
• Ammeter (1)
• In series (1)
(iii) Heat generated through a current carrying conductor is directly
proportional to square of current, resistance of conductor and time
for which current flows in conductor. (1)
/
$H=I^2Rt$ (1)