A portable radio requires an emf of 4.5 V. Olivia has only...

A portable radio requires an emf of 4.5 V. Olivia has only two nonrechargeable $1.5 \mathrm{V}$ batteries, but she finds a larger $6.0 \mathrm{V}$ battery. (a) How can she arrange the batteries to produce an emf of $4.5 \mathrm{V} ?$ Draw a circuit diagram. (b) Is it advisable to use this combination with her radio? Explain.

A portable radio requires an emf of 4.5 V. Olivia has only two nonrechargeable $1.5 \mathrm{V}$ batteries, but she finds a larger $6.0 \mathrm{V}$ battery.
(a) How can she arrange the batteries to produce an emf of $4.5 \mathrm{V} ?$ Draw a circuit diagram. (b) Is it advisable to use this combination with her radio? Explain.

Key Concepts

Series Connection of Batteries

Connecting batteries in series means linking the positive terminal of one battery to the negative terminal of the next. This configuration adds the individual emf values of the batteries together, provided they are all oriented in the same direction. It is a fundamental method for achieving a higher total voltage than that provided by a single cell.

Polarity Reversal for Voltage Subtraction

When batteries are connected in opposite orientations, their voltages do not add normally; instead, they subtract. By reversing the polarity of one battery relative to the others, the net emf becomes the difference between the higher and lower voltages. This principle allows for the adjustment of output voltage by effectively cancelling a portion of the total voltage.

Circuit Diagram Representation

A circuit diagram uses standardized symbols to represent electrical components and their connections. For battery arrangements, symbols include a set of parallel lines (representing the positive and negative terminals) and connecting wires. Such diagrams help visualize how batteries are connected—whether in series, parallel, or with reversed polarity—to achieve a desired net voltage.

Voltage Matching and Device Safety

Electronic devices are designed to operate at specific voltage levels, and supplying a voltage significantly different from what is required can lead to improper operation or permanent damage. Ensuring that the effective voltage provided by a battery arrangement matches the device's specifications is crucial for both performance and safety, as using a mismatched power source can also lead to inefficient energy use or overheating.

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