Main Difference – Conduction vs. Induction
The terms conduction and induction both refer to methods that can cause a current to start flowing in a conductor. The main difference between conduction and induction is that conduction relies only on an electric field, whereas induction relies on a changing magnetic field.
What is Conduction
In electricity, conduction involves a flow of charge carriers in response to an electric field in a conductor. When there is an electric field through a conductor, the free charge carriers in the conductor (for example, the “free” electrons in the case of a metal wire) begin to drift in response to that electric field.
If two conductors are placed in contact with each other, then the electric field can continue from one conductor into the other. If one of the conductors were conducting a current at the beginning, now the second conductor can also start conducting the current. Whenever the electric field across one conductor changes, the electric field across the other conductor also changes. This allows conduction to transfer both direct and alternating currents.
In experiments involving static electricity, charging by conduction refers to transferring charge onto an uncharged object by bringing it into contact with a charged object.
What is Induction
During induction, an object carrying a varying current causes another current to flow. This can happen because any object carrying a current has a magnetic field formed around it. This magnetic field changes whenever the current flowing through the conductor changes.
The magnetic field is present all around the wire. According to Faraday’s Law, if we place a piece of conductor in a region that has a varying magnetic field, an electric field should form on the conductor and this should cause a current to flow in it. So, if we place a second piece of conductor close to a conductor that is carrying a varying current (such as an alternating current), then a current would be induced in the second conductor, as well.
This is the process described as mutual inductance, and it is used to make an A.C. transformer work. The image below helps to illustrate the principle:
How an AC transformer uses induction
Whenever the primary current through the primary coil (shown in red, on the left) changes, the magnetic field around that coil changes. The “transformer core” transports the magnetic field to the secondary coil (shown in blue, on the right). Since this magnetic field is changing, a current is induced on the secondary coil. Notice that no current flows directly from the first coil to the second.
Now imagine just a single coil of wire carrying an alternating current. We have already established that it has a varying magnetic field around it. The coil itself is in its own magnetic field. This means that a current should be induced on the coil whenever its own magnetic field changes. According to Lenz’s law, this current should attempt to oppose any change in the original current. This type of inductance, where a coil of wire resists a change in current through itself is called self-inductance. An inductor is a circuit component used to resist any changes in the current through the circuit (it is usually just a coil of wire). An inductor has no function in D.C. circuits: an opposing current cannot be induced on an inductor unless there is some change in current.
Several different types of inductors
In experiments involving static electricity, charging by induction refers to charging an uncharged object by bringing a charged object close to the uncharged object. The video below demonstrates and explains how an electroscope could be charged both by conduction and induction:
Difference Between Conduction and Induction
What it Means
Conduction involves a flow of electric charge due to an electric field. To conduct a current from one conductor to another, the two conductors should be in contact.
In induction, a current can be made to flow in a conductor by keeping it in the vicinity of another conductor, carrying a constantly varying current.
Variation of Electric or Magnetic Fields
In conduction, current is generated when an electric field passes through the conductor.
In induction, current is generated when a magnetic field changes around a conductor.
Type of Current
Devices relying on conduction can work either with D.C. or A.C. current.
Devices relying on induction can only work with A.C. current: inductors only respond to changes in the current.
Direction of Currents
In conduction, any new currents formed follow the original currents.
In induction, the new currents induced always oppose changes in original currents (Lenz’s law).
In Static Electricity Experiments
Charging by conduction refers to charging an uncharged object by placing it in contact with a charged body.
Charging by induction refers to charging an uncharged object by bringing it close to a charged object, without allowing the two objects to come into contact.
Image Courtesy
“Idealised single-phase tranformer also showing the path of magnetic flux through the core.” by BillC at en.wikipedia (Own work) [CC BY-SA 3.0], via Wikimedia Commons
“Electronic component – various small inductors” by me (Photograph) [CC BY-SA 3.0], via Wikimedia Commons
