Question

A bicycle generator creates $1.5 \,V$ at $15\, km/hr$. The $EMF$ generated at $10\, km/hr$ is

• A. 1.5 volts
• B. 2 volts
• C. 0.5 volts
• D. 1 volts

Answer 1

Answer: (D)

Emf induced, $\varepsilon = Blv$
Here, $\bar{B}, \bar{l}$ and $\bar{v}$ are mutually perpendicular
For given $B$ and $l, \varepsilon \, \propto\, v$.
$\therefore \:\:\:\:\: \frac{\varepsilon_1}{\varepsilon_2} = \frac{v_1}{v_2}$
Here, $\varepsilon_1 = 1.5 \, V, v_1 = 15 \, km /hr = 15 \times \frac{5}{18} m \, s^{-1}$
$v_2 = 10 \, km /hr = 10 \times \frac{5}{8} ms^{-1} , \varepsilon_2 = ?$
So, $\frac{1.5}{\varepsilon_2 }=\frac{15 \times\frac{5}{18}}{10\times\frac{5}{18}} = \frac{3}{2} ;\varepsilon_2 = 1 \, V$