Discussion Overview
The discussion revolves around understanding Ohm's Law in the context of controlling current in a motor circuit. Participants explore the implications of using resistors to limit current and the associated power ratings, as well as the behavior of MOSFETs in series with resistors.
Discussion Character
- Technical explanation
- Debate/contested
- Exploratory
Main Points Raised
- One participant proposes using a 360-ohm resistor to reduce the current from 100 amps to 30 amps in a 12-volt motor circuit, applying Ohm's Law.
- Another participant calculates that the motor's resistance is 0.12 ohms and suggests that to achieve 30 amps, a series resistor of 0.28 ohms would be required, along with a power rating of 252 watts for the resistor.
- There is a correction regarding the formula V * I = R, clarifying that V * I represents power, while V / I gives resistance.
- A question is raised about the behavior of a power MOSFET rated for 50 volts and 17 amps when used in series with resistors of different values, specifically 2.2 ohms and 0.7 ohms.
- Another participant explains the current draw for a 2.2-ohm resistor in a 12-volt circuit and the effects of adding a 0.7-ohm resistor in series, noting that a MOSFET does not generate voltage and can only conduct current when acting as a short circuit.
- A warning is issued about the dangers of high current in vehicle electrics and the potential fire hazards associated with short circuits.
Areas of Agreement / Disagreement
Participants express differing views on the appropriate resistor values and configurations for achieving desired current levels, and there is no consensus on the best approach to take in practical applications.
Contextual Notes
Participants note the importance of understanding the implications of using resistors in motor circuits, including power ratings and the risks associated with high currents, particularly in vehicle applications.
Who May Find This Useful
This discussion may be useful for individuals interested in electrical engineering, circuit design, or those working with motors and power electronics.