AP Physics C Electricity : Using Lenz's Law
Study concepts, example questions & explanations for AP Physics C Electricity
All AP Physics C Electricity Resources
Example Questions
Example Question #201 : Ap Physics C
A wire loop carrying no current is placed near another very long straight wire carrying current 
In which direction will the current induced in the small wire loop flow?
Counterclockwise
No current will be induced in the wire loop
Clockwise
Not enough information is given to solve
Clockwise
The magnetic field due to the long straight wire points into the page (right-hand rule) in the region below it in the picture. The magnitude of this magnetic field is given by:
The magnetic field thus decreases in value with increasing distance, 
According to Lenz's Law, an induced current within the wire loop will counteract this loss of magnetic flux from the straight wire. The magnetic field from the induced current in the wire loop will consequently point in the same direction as that from the current in the straight wire. The right-hand rule for a magnetic field into the page yields an induced current direction in the clockwise direction.
Certified Tutor
All AP Physics C Electricity Resources
