Image

Brushing Up: Ohm Sweet Ohm

March 1, 2004
In 1827, George Simon Ohm, a German physicist, published a paper titled, "The Galvanic Circuit Investigated Mathematically"

In 1827, George Simon Ohm, a German physicist, published a paper titled, “The Galvanic Circuit Investigated Mathematically.” Here, Ohm described a series of experiments in which he measured and analyzed current and voltage through and across various conductive materials. He concluded that in certain materials, current and voltage were directly proportional, related by a constant, resistance, the unit of which is the ohm (Ω).

Ohm's Law

According to Ohm’s law, the voltage V across a current-carrying resistor is the product of the current I and resistance R; V = RI. The corresponding power P dissipated by the resistor is found by substituting V = RI in the standard power equation P= VI, yielding P = (RI)I = I2R.

Resistors at work

A resistor is an electrical component often used to limit current or reduce source voltage powering a load. Industrial applications for resistors — big, tough ones — are quite common, running the gamut from dynamic braking on adjustable-speed drives to reducedvoltage (soft) starting on ac motor-driven conveyors, hoists, pumps, and mill stands. They also include current or torque-limited starting and stopping on equipment powered by dc motors.

Series connection

The equivalent resistance REs of two or more resistors connected in series is the sum of the individual resistances.

REs = R1s + R2s + ... RNs

Parallel connection

The equivalent resistance REp of two or more resistors connected in parallel is the reciprocal of the sum of the reciprocals of each resistance.

REp = 1/(1/R1p + 1/R2p + ... 1/RNp)

Sponsored Recommendations

April 16, 2025
Clean. Compact. Less heat.
April 16, 2025
SEW-EURODRIVE Introduces DR2C motor, IE5 Ultra-Premium Efficiency Motor
March 31, 2025
Unlike passive products - made of simple carbon springs - the bionic prostheses developed by Revival Bionics are propulsive, equipped with a motor and an artificial Achilles tendon...
March 31, 2025
Electric drives are a key technology for the performance of machines, robots, and power tools. Download this guide for an introduction to high-quality mechatronic drive systems...

Voice your opinion!

To join the conversation, and become an exclusive member of Machine Design, create an account today!