Question

Study the diagram carefully and calculate:

(a) the equivalent resistance between (P) and (Q),

(b) the reading shown by ammeter, 

(c) the electrical power between P and Q.

Answer 1

(a) Equivalent resistance: The \(3\ \Omega\) and \(6\ \Omega\) resistors are in parallel:

\[R_{PQ}=\frac{3\times6}{3+6}\]

\[=\frac{18}{9}\]

\[=2\ \Omega\]

(b) Ammeter reading: The two cells provide \(4\ \mathrm{V}\) in series, so:

\[I=\frac{V}{R}\]

\[=\frac{4}{2}\]

\[=2\ \mathrm{A}\]

(c) Power:

\[P=VI\]

\[=4\times2\]

\[=8\mathrm{W}\]