Question

An electric bell takes a current of 0.2 ampere from a battery of 2 dry cells connected in a series each cell has electric motive force of 1.5 volt and an internal resistance of 1.0 ohms . calculate the effective resistive of the cell

Answer 1

solution

current in bell (I)=0.2 A

EMF(E)=1.5 volt

internal resistance(r)=1.0 ohm

total resistance

(R_t)=R_bell + 2r

(R_t)=R_bell + 2$\cdot 1$

R_bell = R_t - 2

total resistance can be calculated as

$R_t=\frac{2E}{I}$

$R_t=\frac{2\times1.5}{0.2}\\=15\Omega$

then

$R_{bell}=15-2\\=13\Omega$

so resistance of bell is 13 ohm .