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In an electric circuit, a call of certain emf provides a potential difference of 1.25 \mathrm{~V} across a load resistance of 5 \Omega. However, it provides a potential difference of 1 \mathrm{~V}across a load resistance of 2 \Omega.
The emf of the cell is given by \frac{x}{10} V. Then the value of x is__________.
 

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        I=\frac{\varepsilon }{\left ( R+r \right )}

WhenR=R_{1}=5\Omega, IR=1.25

                                    I=I_{1}=0.25A

WhenR=R_{2}=2 \Omega$, IR $=1 \mathrm{~V}

                                      I=I_{2}=0.5A

I_{1}=\frac{\varepsilon }{\left ( 5+r \right )}=0.25

I_{2}=\frac{\varepsilon}{(2+r)}=0.5

\frac{\varepsilon }{\left ( 2+r \right )}=\frac{2\varepsilon }{5+r}

5+r=4+2r

        r=1\Omega

\varepsilon =1.5v=\frac{15}{10}\: V

\therefore x=15

 

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vishal kumar

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