A loop of wire is lying flat on a tabletop. A uniform magnetic field is directed vertically UPWARDS such that it is perpendicular to the tabletop (and the loop). Beyond the edge of the table, the magnetic field is zero. Imagine that you are looking DOWN on the loop from above. Which of the following statements are true about the induced EMF in the wire loop? You will have to refer to Lenz's Law in order to determine the direction of the induced current.
True/False if the magnetic field suddenly decreases, the induced current will be in a clockwise direction
True/False if you keep the loop on the table, but pull it to the left, the induced current will be in a counter-clockwise direction
True/False if the loop suddenly grows in size, the induced current will be in a clockwise direction
True/False if you pull the loop out of the field (by sliding it off the table), the induced current will be in a clockwise direction
True/False Lenz's Law states that the induced current always leads to a magnetic field that OPPOSES the change in magnetic flux
To determine the direction of the induced current in the wire loop, we can use Lenz's Law, which states that the induced current always opposes the change in magnetic flux. Here's how we can analyze each statement:
1. If the magnetic field suddenly decreases, the induced current will be in a clockwise direction. (True)
According to Lenz's Law, when the magnetic field decreases, the induced current in the loop will create a magnetic field that opposes this decrease. To do so, the current must flow in a direction that creates a magnetic field in the same direction as the original magnetic field. This can be achieved by a clockwise current flow in the loop.
2. If you keep the loop on the table but pull it to the left, the induced current will be in a counterclockwise direction. (True)
When the loop is pulled to the left, the magnetic flux through the loop decreases. Lenz's Law states that the induced current will oppose this change, so the current will flow in a direction that creates a magnetic field that opposes the decrease in flux. By applying the right-hand rule, we can determine that a counterclockwise current in the loop will produce a magnetic field in the upward direction, opposing the decrease in magnetic flux.
3. If the loop suddenly grows in size, the induced current will be in a clockwise direction. (False)
When the loop grows in size, the magnetic flux through the loop increases. Lenz's Law states that the induced current will oppose this change. In this case, to counteract the increase in flux, the induced current must flow in a direction that produces a magnetic field in the downward direction. Therefore, the induced current will actually be in a counterclockwise direction.
4. If you pull the loop out of the field (by sliding it off the table), the induced current will be in a clockwise direction. (False)
When the loop is pulled out of the magnetic field, the magnetic flux through the loop decreases. Following Lenz's Law, the induced current will oppose this change. To do so, the current will flow in a direction that creates a magnetic field in the upward direction, counteracting the decrease in flux. Therefore, the induced current will be in a counterclockwise direction.
5. Lenz's Law states that the induced current always leads to a magnetic field that opposes the change in magnetic flux. (True)
This statement accurately summarizes Lenz's Law. The induced current in a conductor always creates a magnetic field that opposes the change in magnetic flux through the loop. This principle is an important consequence of conservation of energy and is used to determine the direction of the induced current in various situations.
Therefore, the correct answers are:
1. True
2. True
3. False
4. False
5. True