Question Video: Identifying the Current Used in a Transformer | Nagwa Question Video: Identifying the Current Used in a Transformer | Nagwa

Question Video: Identifying the Current Used in a Transformer Physics • Third Year of Secondary School

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What kind of current are transformers used with?

02:31

Video Transcript

What kind of current are transformers used with? (A) Direct current, (B) alternating current, (C) both alternating current and direct current.

This question is asking us to identify the type of current used in transformers. Let’s start by reminding ourselves of what a transformer is. A transformer consists of two coils of wire, or solenoids, connected through a common core. A transformer uses electromagnetic induction to transfer energy between the solenoids. Electromagnetic induction is a process where changing currents can induce magnetic fields. Similarly, changing magnetic fields can produce electric currents.

To see how this works in transformers, let’s say that this coil has a current in it, which we’ve labeled 𝐼 p. We’ll call this coil the primary coil and the other coil the secondary coil. If the current in the primary coil were to change at all, then a magnetic field would be induced in the core of the transformer. When a magnetic field is induced by the current in the primary coil, the magnetic field experienced by the secondary coil changes. This changing magnetic field produces a current in the secondary coil. This is the process used by all transformers.

Electromagnetic induction allows energy from the current in the primary coil to be transferred to the secondary coil. But what does this tell us about the kind of current used? Well, recall that for electromagnetic induction to occur, the current in the coils must be changing, because only a changing current can induce a magnetic field.

Now that we know this, we can go through our options: direct current, alternating current, and both alternating current and direct current. A direct current is one that does not change in magnitude or in direction. So, we can rule out option (A). The magnitude of an alternating current is continuously changing, and the direction of the current periodically reverses, too. So, an alternating current is definitely a type of current that could be used in transformers since it’s always changing. This means option (B) is a strong contender for the right answer. But let’s check option (C) just to be sure.

A single current cannot be both alternating and direct at the same time. And if there is an alternating current in the primary coil, then the same type of current will be produced in the secondary coil. A transformer cannot have both alternating current and direct current at the same time, and we can rule out option (C). This means the correct answer must be option (B). Transformers are used with alternating current.

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