General Question about circuits

  • Thread starter Thread starter fredrogers3
  • Start date Start date
  • Tags Tags
    Circuits General
Click For Summary
SUMMARY

The discussion centers on understanding the behavior of current in circuits, particularly when dealing with inductors. When a switch is opened in a circuit containing an inductor, the current does not instantly turn negative; instead, an induced electromotive force (emf) arises, opposing the change in current as per Lenz's Law. This phenomenon can lead to observable effects, such as sparks when disconnecting devices from power sources. The confusion often arises from the interpretation of current direction and the effects of inductance during circuit interruptions.

PREREQUISITES
  • Basic understanding of circuit diagrams and current direction
  • Familiarity with inductors and their properties
  • Knowledge of Lenz's Law and electromagnetic induction
  • Experience with circuit analysis techniques
NEXT STEPS
  • Study Lenz's Law in detail to understand its implications in circuit behavior
  • Learn about inductive kickback and its effects on circuit components
  • Explore practical examples of circuits with inductors and switches
  • Investigate the role of induced emf in various electrical applications
USEFUL FOR

Students studying electrical engineering, hobbyists working with circuits, and professionals seeking to deepen their understanding of inductive behavior in electrical systems.

fredrogers3
Messages
40
Reaction score
0

Homework Statement


I have a general question concerning circuits. I am a bit confused as to how to determine when the current is negative. For instance, on circuit diagrams, we are shown arrows that indicate the positive direction of current. Then, when we open the switch on the circuit, the current through an inductor all of a sudden turns negative. I thought that such a discontinuous change was not possible. In general, how can I determine when the sign of the current turns negative?


Homework Equations


See Above


The Attempt at a Solution


See Above
 
Physics news on Phys.org
It is not the current that all of a sudden turns negative through an inductor when a switch gets opened. Just the opposite: If current flowed through a coil earlier, and we break the circuit so the current would cease, an induced electromotive force appears in the coil which maintains the current for a while: opposes the change of current. (Lenz's Law) Sometimes you even see a spark when you plug out a heater or hair-dryer from the socket.

ehild
 
Last edited:

Similar threads

Determining Inductance L in an LC Circuit
  • · Replies 5 ·
Replies
5
Views
2K
Calculation of current in driven series RLC circuit
  • · Replies 8 ·
Replies
8
Views
3K
Combined tensions of an RLC series circuit with AC current
  • · Replies 3 ·
Replies
3
Views
1K
Write boolean expression describing this circuit
  • · Replies 4 ·
Replies
4
Views
1K
Why is there a resistor in a MOSFET-based inverter?
  • · Replies 9 ·
Replies
9
Views
2K
Why do the headlights on the car become dim when the car is starting?
  • · Replies 4 ·
Replies
4
Views
2K
Determine the Thevenin equivalent circuit
  • · Replies 2 ·
Replies
2
Views
2K
Current flowing through a resistor in an RRL DC circuit
  • · Replies 5 ·
Replies
5
Views
2K
What is the unknown circuit element in RLC circuit given plot of V, I?
  • · Replies 4 ·
Replies
4
Views
1K
Understanding a very simply RL circuit
  • · Replies 1 ·
Replies
1
Views
1K