Recent content by pkc111

so a 6V battery can have an immediate jump to 10 ohm (3V) internal resistance drawing 0.4 amp?

10 ohms

Ok..I think its becoming a little bit clearer. The 5V to 3V drop in the net motor supply voltage when the motor is stopped with fingers still puzzles me. Are we saying that the rise in voltage expected by absence of a back-emf in rotor when stopped with fingers, is more than made up for by a...

So my DC motor with a 6V battery attached gives a 5V PD reading across the motor terminals. When the rotor is held still with fingers it reads 3V...whyso? I thought the voltage would go up when held due to the absence of a back emf. Also when I use the motor shaft to drive an identical motor...

Thank you! I think I may try a battery instead to remove some variables :)

and would I be better off trying to quantify a motor's back emf with a battery rather than a transformer power supply?

Thanks, So how would I model (in a spreadsheet )the predicted net voltage across a small 4 V DC motor hooked up to a laboratory power pack set at 2V when the motor is slowed down to different % max speeds by finger resistance?

Hi there, I have done an experiment measuring the voltage across the terminals of a dc motor, whilst running and then by holding it with my fingers to stop it. Done as demo for my high school class. The voltage reading was higher when the motor was running, which was against my expectations as...

Pearson Physics 12 states: "When the light sources have the same intensity but different frequencies, they produce the same maximum current" However, Phet Simulation Photoelectric Effect seems to show that photocurrent changes with light frequency (eg see below for different photocurrents at...

The attached probem tricked me because the answer is apparently D and not A. Presumably because the magnetic field is weaker with 2 bar magnets joined N/S compared to a single bar magnet. So this seems to be a gap in my knowledge as to the resulting strengths of magnets joined together. Are...

Ok then does it sound better to replace "parallel" with "which have a component that is parallel"?

Every force has to have a non-zero component parallel to the motion to contribute to work in that direction ie W=Fscostheta.

Your definition of "work is energy" and "energy is work" contradicts many published definitions of the meaning of "work" in physics. https://en.wikipedia.org/wiki/Work_(physics) "In physics, work is the energy transferred to or from an object via the application of force along a displacement."

This is my latest attempt at trying to summarise but I feel there maybe a mistake in the wording. Any help would be appreciated. Thanks.