Final answer:
The correct option is b. transformer. A common application of mutual inductance is found in a device called a transformer. Transformers are commonly used to transform voltages from one value to another.
Step-by-step explanation:
The common application of mutual inductance is found in a device called a transformer. Mutual inductance is the effect of Faraday's law of induction for one device upon another, such as the primary coil transmitting energy to the secondary in a transformer. Transformers are commonly used to transform voltages from one value to another.
For example, many cell phones, laptops, power tools, and small appliances have a transformer built into their plug-in unit that changes the alternating current (AC) voltage into whatever voltage the device uses.