Lenz's Law: Which Way Does the Induced Current Go?

Faraday’s law gives you the size of the induced EMF and says nothing about its direction. Lenz’s law supplies the direction, and it is always the same answer: the induced current opposes the change that made it. Set the pole and the motion and this tells you which way the current runs, which pole the loop presents, and why.

Last updated 11 Nov 2026

Pole, motion, and the direction of the induced current

oppose the change, never help it

Which pole of the magnet faces the loopField lines leave a north pole and return to a south pole, so with the north pole facing the loop the field at the loop points away from you and through it — into the page in the right-hand half of the diagram. With the south pole facing you, it points back out at you.

What the magnet is doingOnly relative motion matters. Moving the loop towards a stationary magnet gives exactly the same answer as moving the magnet towards a stationary loop. A magnet held still next to the loop, however strong, induces nothing at all, because nothing is changing.

Is the loop a complete circuit?An open loop still has an EMF across the gap — the EMF is driven by the changing flux and does not care whether charge can go anywhere. What it does not have is a current, and therefore no opposing field and no force on the magnet. This is the distinction between EMF and current that examiners probe most often.

On the left, a side view: the magnet with its poles, an arrow for the way it is moving, the field arrows it sends through the loop, and the loop seen edge on. On the right, the same loop face on, as you would see it looking through the magnet, with the induced current drawn in green. Swap the pole or swap the motion and the green arrows turn round; swap both and they turn back. Open the loop and the current vanishes while the field arrows stay.

Anticlockwise, as you look at the loop through the magnetExample

A bar magnet with its north pole facing a closed loop, moving towards it

Three steps, in this order, every time

1. which way does the field thread the loop? · 2. is that flux rising or falling? · 3. the induced current makes a field that OPPOSES the change

step 1: field lines come out of a north pole. North facing the loop means the field at the loop points away from you and through the loop. South facing the loop means it points back towards you. Get this one wrong and the other two steps are flawless and useless
step 2: moving the magnet closer makes the flux bigger; moving it away makes it smaller. Nothing else about the motion matters — not the speed, which only changes the size of the EMF, and not whether the magnet or the loop is the thing that moves
step 3: the induced current’s own field points the way that fights the change: the same way as the original flux if that flux is falling (to prop it up), the opposite way if it is rising (to hold it down). Then the right-hand grip rule turns that field direction into a current direction
the force, free: once you know the current, you know the force without any more work. An approaching magnet is always repelled and a receding magnet is always attracted, for every pole and both directions. Lenz’s law opposes the CHANGE, which is the relative motion
why not the other way: because an induced current that helped the change along would make the magnet accelerate by itself, which would induce a larger current, which would accelerate it more. You would have free energy. Lenz’s law is conservation of energy wearing a direction rule

Worked example

A bar magnet with its north pole facing a closed loop, moving towards it
WHICH WAY DOES THE FIELD GO THROUGH THE LOOP? Lines leave a north pole, so with north facing the loop the field at the loop points away from you — into the page as the right-hand half of the diagram draws it.
IS THAT FLUX RISING OR FALLING? The magnet is getting closer, so the field at the loop is getting stronger and the flux into the page is rising.
WHAT MUST THE INDUCED FIELD DO? Oppose that rise. So inside the loop the induced field must point out of the page, back towards you.
TURN THAT INTO A CURRENT. Right-hand grip rule: point your right thumb out of the page at yourself and your fingers curl anticlockwise. That is the induced current, and it is the answer.
CHECK IT WITH THE POLES. An anticlockwise current seen from your side makes the loop's near face a north pole. North faces north, so the loop pushes the magnet back — which is exactly what Lenz's law says must happen to an approaching magnet, whichever pole it leads with.
NOW REVERSE ONE THING AT A TIME. Pull the same magnet away instead and every step flips once: the current becomes clockwise, the loop's near face becomes a south pole, and the magnet is pulled after it. Reverse the pole instead and it flips once too. Reverse both and you are back where you started, which is the quickest way to check an answer in an exam.

All four combinations, and the force in every one

The current direction changes in all four rows, and the last column does not: an approaching magnet is always pushed back and a receding magnet is always pulled after. That column is Lenz’s law itself, and it is the one to remember — if you can only hold one thing in your head under exam conditions, hold on to “the loop always tries to stop the magnet moving” and work the current direction out from it.
Pole facing the loop	Motion	Induced current, as you look at it	Loop’s near face	Force on the magnet
North	Approaching	Anticlockwise	North	Repelled
North	Receding	Clockwise	South	Attracted
South	Approaching	Clockwise	South	Repelled
South	Receding	Anticlockwise	North	Attracted

Opposition, not creation — and why that is conservation of energy

Lenz’s law has exactly one content: the induced effect opposes the change that caused it. Cambridge 9702 words the outcome as “the induced e.m.f. is in such a direction as to oppose the change producing it”; CBSE’s Unit IV names it in one line beside Faraday’s laws. Everything else — which way the current goes, which pole the loop shows, whether the magnet is pushed or pulled — follows from that sentence and a right hand.

Work it in three steps and it never fails. First, which way does the magnet’s field thread the loop? Lines leave a north pole, so a north pole facing the loop sends field away from you through it. Second, is that flux growing or shrinking? Closer means growing. Third, the induced current’s own field must fight the change: it points the same way as the existing flux if the flux is falling, the opposite way if it is rising. Then curl your right hand to turn a field direction into a current direction. Students who get this wrong almost always get step one wrong and the rest right.

The force is free once you have the current, and it never changes sign. Look at the table: the current direction changes in all four rows, and the force column does not. An approaching magnet is repelled; a receding magnet is attracted. That is the whole law, and it is worth more under exam pressure than the current direction, because you can get back to the current from it.

Why opposition and not help? Because the alternative creates energy from nothing. Suppose a dropped magnet were attracted by the loop it was approaching. It would accelerate, inducing a bigger current, accelerating more — gaining kinetic energy and delivering electrical energy at the same time, from nowhere. Lenz’s law is conservation of energy expressed as a direction. It is also why a magnet dropped down a copper pipe falls slowly, why a generator gets physically harder to turn as you draw more current from it, and why eddy-current brakes on a train have nothing to wear out. For the size of the EMF this direction belongs to, see Faraday’s law and the induced EMF; for the field the induced current itself makes, the field of a coil.

Frequently asked questions

Does it matter whether the magnet moves or the loop moves?

No. Only the relative motion matters, and only through the flux it changes. Moving the loop towards a stationary magnet gives the same induced current as moving the magnet towards a stationary loop. Hold them both still and nothing happens at all, however strong the magnet is.

What does ‘clockwise’ mean here? Clockwise from where?

From your side — looking at the loop through the magnet, as the right-hand panel of the diagram draws it. Direction answers in this topic are meaningless without a stated viewpoint, and examiners expect you to state one. Walk round and look at the loop from the other side and the same current is anticlockwise.

Is there an EMF if the loop is broken?

Yes, and this page says so: choose the open-loop option and you get an EMF with no current. The changing flux drives an EMF regardless of whether charge can circulate. What you lose by breaking the loop is the current, and with it the induced field and the force on the magnet — which is why an open-circuited generator is easy to turn and a short-circuited one is very hard.

How does Lenz’s law relate to the minus sign in Faraday’s law?

They are the same statement. ε = −N dΦ/dt, and the minus sign is Lenz’s law written in algebra: a rising flux gives a negative EMF in the right-handed sense about the flux direction, which is the sense that opposes the rise. The minus sign carries no magnitude information at all, which is why so many worked solutions quietly drop it and quote the size.

Does Lenz’s law mean the induced current always flows the same way?

No — it flows whichever way opposes the particular change. The table above has it anticlockwise in two rows and clockwise in two. What is always the same is the effect: the force on the magnet opposes its motion in all four cases.

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References

Annual Syllabus, Class XII, Physics, Code 42, Session 2025-26, Central Board of Secondary Education, edustud.nic.in/edu/SYLLABUS_2025_26/12/12_Physics_EM.pdf (read 11 November 2026). The board’s own document, cited and not endorsed by it. Unit I Chapter 1 asks for “Electric flux, statement of Gauss’s theorem and its applications to find field due to infinitely long straight wire, uniformly charged infinite plane sheet and uniformly charged thin spherical shell (field inside and outside)”. Unit III Chapter 4 asks for “force on a moving charge in uniform magnetic and electric fields”, “torque experienced by a current loop in uniform magnetic field” and “Current loop as a magnetic dipole and its magnetic dipole moment”. Unit IV Chapter 6 is one line and covers three of this batch’s records: “Electromagnetic induction; Faraday’s laws, induced EMF and current; Lenz’s Law, Self and mutual induction”. The Hall effect is not in this document.
Syllabus: Cambridge International AS & A Level Physics 9702, for examination in 2025, 2026 and 2027, Cambridge Assessment International Education, cambridgeinternational.org/Images/664565-2025-2027-syllabus.pdf (read 11 November 2026). Cited for outcomes a Cambridge candidate is examined on that the Indian board words differently or omits. 20.3.3: “understand the origin of the Hall voltage and derive and use the expression V_H = BI /(ntq), where t = thickness”. 20.3.4: “understand the use of a Hall probe to measure magnetic flux density”. 20.5.2: “recall and use Φ = BA”. 20.5.3: “understand and use the concept of magnetic flux linkage”. 20.5.4 asks candidates to explain experiments demonstrating “that the induced e.m.f. is in such a direction as to oppose the change producing it”. 20.5.5: “recall and use Faraday’s and Lenz’s laws of electromagnetic induction”. Note that induction is topic 20.5 here and not a topic of its own; topic 21 is alternating currents. The copy read was retrieved in two parts and the last 19,825 characters were not read, so nothing is claimed about what is on the data-and-formulae sheet.
University Physics Volume 2, chapters 11 and 14, OpenStax, Rice University (openstax.org/books/university-physics-volume-2, key-equations pages read 11 November 2026). An openly licensed university text, cited here because the coaching sites that dominate searches for this topic are not citable and mostly copy one another. Chapter 11 gives the radius of a charged particle’s path as r = mv/(qB), its period as T = 2πm/(qB), the Hall potential as V = IBl/(neA), the drift velocity in crossed fields as v_d = E/B, the magnetic dipole moment as μ = NIA and the torque as τ = μ × B. Chapter 14 gives L_solenoid = μ₀N²A/l, NΦ = LI, ε = −L dI/dt, M = N₂Φ₂₁/I₁ = N₁Φ₁₂/I₂ and U = ½LI². Neither key-equations page lists a cyclotron frequency or a field energy density, so those two are stated here from the definitions and not attributed to this source.