A portable emergency radio beacon uses a power source consisting of three series-connected… — Armed Services Vocational Aptitude Battery (ASVAB)

A portable emergency radio beacon uses a power source consisting of three series-connected DC cells: a primary lithium cell with an electromotive force (EMF) of $3.6\text{ V}$ , a standard cell with an EMF of $1.5\text{ V}$ , and a photovoltaic booster cell with an EMF of $0.9\text{ V}$ . When all three cells are wired in a series-aiding configuration, what is the total electromotive force supplied to the beacon?

A
$3.6\text{ V}$
$6.0\text{ V}$ Answer
C
$6.0\text{ A}$
D
$1.2\text{ V}$

Answer

The total electromotive force supplied to the beacon is

6.0\text{ V}

When multiple direct-current sources are connected in a series-aiding configuration, their individual electromotive forces (EMFs) add algebraically. Summing the three cell ratings gives

3.6\text{ V} + 1.5\text{ V} + 0.9\text{ V} = 6.0\text{ V}

Step-by-Step Solution

Identify the individual electromotive force (EMF) values of the series-connected sources.

E_1 = 3.6\text{ V}

E_2 = 1.5\text{ V}

, and

E_3 = 0.9\text{ V}

Extracting the component voltages is necessary to determine the overall potential difference across the power source.

Apply the rule for DC voltage sources connected in series-aiding polarity (

E_{\text{total}} = E_1 + E_2 + E_3

E_{\text{total}} = 3.6\text{ V} + 1.5\text{ V} + 0.9\text{ V} = 6.0\text{ V}

When cells are wired series-aiding (positive terminal of one cell connected to the negative terminal of the next), their individual electromotive forces combine additively.

Key Concept

Series-Aiding Electromotive Force (EMF) Summation

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