Question Video: Identifying Sources of Alternating Current | Nagwa Question Video: Identifying Sources of Alternating Current | Nagwa

# Question Video: Identifying Sources of Alternating Current Science

A company is making circuits. They need their circuits to have an electric current that periodically reverses direction. What is the best choice for a source of electric current?

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### Video Transcript

A company is making circuits. They need their circuits to have an electric current that periodically reverses direction. What is the best choice for a source of electric current? Is it (A) a chemical battery, (B) a dynamo, or (C) either a dynamo or a chemical battery?

This question asks us for what can supply an electric current that periodically changes direction. We’ve been asked to choose between a chemical battery, a dynamo, or both as a power source. Let’s now think about which option is the best answer.

We know that chemical batteries only produce direct currents, since a battery produces a potential difference between its terminals. The potential difference produces a current in from one terminal to the opposite terminal. The only way to reverse the direction of the current supplied to a circuit by a chemical battery is to reverse the connections of the circuit to the battery terminals.

A dynamo is a machine containing a coiled length of conducting wire that rotates in between the opposite poles of a magnet. This induces an electric current in the coil. For one complete rotation of the coil of a dynamo, the current induced in the coil changes direction from its original direction to the opposite direction to its original direction and then back to the opposite direction. If the coil rotates uniformly, the direction of the current changes periodically. It is easier to uniformly rotate a coil than to repeatedly reverse the connections of a circuit to the terminals of a battery.

So, our correct option is option (B) a dynamo.