# Direction of EMF and Induced current through the circuit When the circuit shown above is moved with a constant velocity to the left I know that B is going to have the higher potential.

And I believe that the current flows clockwise that is in the sense of AEDCB.

But my tutor says that the current flows in the sense ABCDE,saying that it is similar to having a battery across BD with the positive terminal at B instead of the half loop BCD with the magnetic field..

I am very confused with this matter. Am I correct or is my tutor correct?

## 3 Answers

Since $$\mathbf{v}$$ is to the left and $$\mathbf{B}$$ is into the page, $$\mathbf{v}\times\mathbf{B}$$ is towards the bottom of the page.

Thus, a mobile positive charge would flow clockwise (AEDCB) around the circuit and so the electric current is clockwise ('up' through the resistor). Recall that the direction of electric current is in the direction of positive charge flow.

However, your tutor may be referring to electron current which is in the opposite direction of electric current (electrons are negatively charged). The electron current is thus counter-clockwise (ABCDE).

Short version is: Your Tutor is right, but his method is wrong.

So, you are trying to find the direction of the current, and you already have the direction of the magnetic and the force. Note that it is induced current, so you could use Fleming's right hand rule. That means F(the force) is to the left and B the, magnetic field (the x) is through the page(inwards). Using the right hand rule this means that the current is downwards, so take it as down E to A, meaning its clockwise.

Now when your tutor is . talking about the battery, that requires the left hand rule. So in this your trying to confirm F, which you know is left. your B(Magnetic field) is down. Making your current up from B to D.

However your tutors method isn't a great method to use. Left hand rule is usually meant to determine the direction of the force produced by magnetic field and electric current. You're trying to find the induced current, hence its more appropriate to use right hand rule, which is typically use for generators.

I hope you find this useful

• Can you please make this clear.Is the current flowing in the direction AEDCB or ABCDE? – AfiJaabb Jul 12 at 10:22
• My bad, It’s ABCDE – Aakash Mehta Jul 12 at 10:23
• But doesnt it defy lenz law.The flux inwards is reducing and the current should flow in a way to increase the Inward flux right.And also when this setup is pulled outwards to the left the force on the circular part should be to the right.This could happen only if the current flows in the direction DCB right? – AfiJaabb Jul 12 at 10:30
• I suppose you mean current is flowing clockwise.Yeah that's what I am suggesting. – AfiJaabb Jul 12 at 10:39
• Oh no, I’m so sorry it is AEDCB. The flowing of the current is influenced by the magnetic field produced by the conductors which is clockwise. – Aakash Mehta Jul 12 at 10:54

Before starting the answer one you can replace BCD with BC to easily understand ,let for understanding the direction we will apply lenz law that is current induced in a coil in such fashion that it will oppose the cause ,as flux in the coil is decreasing as it is move toward left so current will be in clockwise direction to oppose decrease in current it mean your TUTOR IS RIGHT now coming to your question that B should be at higher potential yiu can simply understand it by lorentz force equation F=QVB there is cross product between V and B that is when your teacher talk about battery yiu can simply derive polarity use right hand palm rule put right hand finger in direction of flux your thumb will indicate velocity and and point that faces palm will be at higher potential YOUR TEACHER IS is simply talking about electron because in this equation q replace by e which is counter or anti clockwise