A fuse is a short piece of wire made up of a material of high resistivity and of low melting point, So that it may easily melt due to overheating due to the excessive flow of electric current.






$\therefore \ \text{I}=\frac{96000}{3600}=\frac{80}{3} \ \text{A}$
$\text{H}=50\times\frac{80}{3}\times60\times60=4.8\times10^6 \ \text{J}$
Therefore, the heat generated is 4.8 x 106 J.$\text{W} = \text{V} \times \text{Q}$
$\text{w} = 20\times5 =100$
$\text{V} = \frac{\text{W}}{\text{Q}}$
$\text{W} = \text{V} \times \text{Q}$
$\text{W} = 30\times5 = 150$
$\frac{1}{\text{Req}}=\frac{1}{\text{R}}+\frac{1}{\text{R}}+\frac{1}{\text{R}}........\text{N time}$
$\frac{1}{\text{Req}}=\frac{\text{N}}{\text{R}}$
$\therefore\bigg(\text{Req}\bigg)_2=\frac {\text{R}}{\text{N}}$
$\therefore\frac{(\text{Req})}{(\text{Req})_2}=\frac{\text{NR}\times\text{N}}{\text{R}}=\text{N}^2$


So, Rs1 = 4 + 8 = 12
Similary R2 and R3 are in series
Rs2 = Q + 4 = 12
Now Rs1 and Rs2 are in || combination
So, $\frac{1}{\text{RP}}=\frac{1}{\text{12}}+\frac{1}{\text{12}}=\frac{1}{\text{12}}=\frac{1}{\text{6}}$
RP = 6
So, Req = $6\Omega$
$\text{W}_\text{B}= -\frac{2\text{C}}{5}\text{C}-\frac{1}{5}\text{C}=-\frac{3}{5}\text{C}$
Total Work Done is W = WA - WB$\text{W} = -\frac{2}{5}\text{C} - \frac{1}{5}\text{C} = -\frac{3}{5}\text{C}$
$\text{W} = \frac{\text{q}}{\text{v}}$
At Point A,$\text{WA} = \frac{2\text{C}}{10} = \frac{1}{5}\text{C}$
$\frac{1}{\text{R}'}=\frac{2}{\text{R}} +\frac{2}{\text{R}}$
$\text{R’}=\frac{\text{R}}{4}.$
$\frac{1}{\text{R}}=\frac{1}{\text{R}1}+\frac{1}{\text{R}1}$
$=\frac{1}{10}+\frac{1}{10}$
$=\frac {2}{10} \text{ohms,}$
$\text{R} = 5 \text{ohms.}$
$\text{R}=\frac{120}{2.4}=50\ \text{ohm}$
In second case, V = 240 volt, R = 50 ohm V = IR 240 = I × 50 I = 4.8amp.$\therefore\text{H}=(15)^{2}\times500\times1800\text{J}$
$\text{H}=225\times500\times1800\text{J}$
$\therefore\text{H}=20.25\times10^{7}\text{J}$
Thus Total heat produced by the heater is 20.25 × 107 J in 30min due to flow of 15A currentRate of heat developed $=\frac{\text{H}}{\text{t}}=\frac{\text{I}^2\text{Rt}}{\text{t}}$
= 152 × 8 = 225 × 8 = 1800 Js-1.


$\text{I}=\frac{9}{13.4}$
$\text{I}=0.67\ \text{amp}$
$\frac{100}{4}=\text{I}^2$
I = 5 amp V = IR V = 5 × 4 = 20V