## College Physics (4th Edition)

(a) $emf = 7.0~V$ (b) $R = 17.5~\Omega$
(a) We can find the equivalent $emf$: $emf = 3.0~V+3.0~V+2.5~V-1.5~V$ $emf = 7.0~V$ (b) We can find the value of the resistor: $emf = I~R$ $R = \frac{emf}{I}$ $R = \frac{7.0~V}{0.40~A}$ $R = 17.5~\Omega$