In a straight conducting wire, a constant current is flowing from left to right due to a source of e

Q: Why does the induced current flow in the same direction?

According to Lenz's Law, the induced current opposes the change that caused it. Since the original current is decreasing, the induced current flows in the same direction to try and maintain the current level.

Q: Can a straight wire have self-inductance?

Yes, every current-carrying conductor creates a magnetic field around itself, which means it has some self-inductance, although it might be very small for a straight wire compared to a coil.

Q: What if the current was increasing instead?

If the current was increasing, the induced current would flow in the opposite direction (right to left) to oppose the increase.

Q: Why is the answer 'or zero'?

In ideal theoretical problems, a straight wire might be considered to have zero self-inductance. Without inductance, there is no induced emf, and thus no induced current.

Q: Does this violate conservation of energy?

No, the energy for the induced current comes from the energy stored in the magnetic field of the wire before the switch was turned off.

Question

In a straight conducting wire, a constant current is flowing from left to right due to a source of emf. When the source is switched off, the direction of the induced current in the wire will be......

Sigma Percentile · Accepted Answer

### The Setup: A Steady Flow

Imagine a straight conducting wire. Initially, a constant current $I$ is flowing through it from left to right due to an external source of electromotive force.

Everything is in a steady state, and a constant magnetic field surrounds the wire.

### The Disruption: Switching Off

Now, what happens when we suddenly switch off the source? The current doesn't just vanish into thin air. It starts to decrease rapidly towards zero.

This is where the magic of electromagnetism kicks in. According to **Lenz's Law**, nature abhors a change in magnetic flux. The decreasing current causes a decreasing magnetic field, which in turn induces an electromotive force $\varepsilon$ in the wire.

### The Resistance: Lenz's Law in Action

The induced electromotive force is given by the equation $\varepsilon = -L \frac{dI}{dt}$, where $L$ is the self-inductance of the wire.

Because the current is decreasing, $\frac{dI}{dt}$ is negative, making the induced emf positive. This means the induced emf will try to push a current in the **same direction** as the original current to oppose the decrease.

Therefore, the induced current will flow from **left to right**, desperately trying to keep the original current alive.

### The Catch: The Role of Inductance

But wait, there is a subtle catch here! This entire phenomenon relies on the presence of self-inductance $L$.

If we consider a perfectly ideal straight wire with absolutely zero self-inductance ($L = 0$), then the induced emf $\varepsilon$ will be exactly zero, regardless of how fast the current changes.

In such an idealized scenario, there would be no induced current at all.

### The Final Verdict

Taking both practical and ideal scenarios into account, the induced current will either flow from **left to right** (if there is some inductance) or it will be **zero** (if the inductance is perfectly zero).

This dual possibility perfectly captures the essence of the problem!

Animated Solution for Physics - Electromagnetic Induction: In a straight conducting wire, a constant current is flowing from left to right due to a source of emf. When the source is switched off, the direction of the induced current in the wire will be......

Visualized Solution

$Initial Setup$

$Lenz’s Law$

$Direction of Induced Current$

$Role of Inductance$

$Conclusion$

The Sigma Insight: Lenz's Law

The Setup

The Disruption

The Resistance

The Catch

The Final Verdict

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