Ask-a-Physicist by Topic

Electricity & Magnetism

Never-ending light in a room full of mirrors

If you had a light in a room which was entirely sealed with mirrors, then switched the light off, would the room stay lit?

Would the light just keep reflecting off the mirrors?

Would it slow down? Perhaps to the point where it is no longer visible?


Find out the answer »

Lifting with Static Electricity

Can electricity (static or not) be used to move very large objects? Could you somehow control a sufficiently strong electrical current through the air or across a surface to lift a log or a car? Are there certain objects it could lift and certain ones it couldn't?


Find out the answer »

Super-Kamiokande neutrino detector in Japan. Image Credit: Univ. of Tokyo I am lost about neutrinos. I thought a neutrino was just a neutrino since it is neutral. What are the differences between electron, muon, and tau neutrinos?
Find out the answer »

Water as a dipole showing the slight charges Since water molecules are negatively charged on one side and positive on the other, can you freeze a container of water which you place in a magnetic field and create an ice-magnet?
Find out the answer »

sandanimation

I built a sand art box for performing sand art but I have a problem. The sand I use keeps bouncing around on the glass as opposed to being pencil thin. How or what kind of sand can I use to remedy that?


Find out the answer »

Crank

How can you make electric currents from magnets?


Find out the answer »

array How is the photoelectric effect used to produce a current in a photovoltaic cell?
Find out the answer »

microwave Why does aluminum foil spark in the microwave? - BB, Iowa City, IA
Find out the answer »

switches Some lights in my home are controlled by two different switches. How is this possible? - V
Find out the answer »

cables Why is it that when you severely kink an Ethernet cable, you can no longer transmit data on it? That cable contains 4 twisted pairs of copper wires and kinking the cable doesn't break or short out those wires. Why should the kink matter? - DB, Evansville, Indiana
Find out the answer »

toothbrush My electric toothbrush charges up by sitting in its base unit. There is no metal-to-metal contact—only plastic-to-plastic. Since the plastic is non-conductive, how does it charge? – RS
Find out the answer »

storms After a tropic thunderstorm, why does it feel so nice to breath? - WM, Kota Baru, Kelantan, Malaysia
Find out the answer »

brightness For a science project, I made a parallel circuit and a series circuit. Each is powered by a 6.3-volt battery and has three six-volt lights on it. Why is the series circuit so much dimmer than the parallel circuit? - ML, Woodbridge, CT
Find out the answer »

Generator Why does an electric generator slow down when you begin to use the power it is generating? – WV, Waverley, South Africa
Find out the answer »

motor If you coupled a motor to a generator and connected them to the same power source, would the generator be able to recycle wasted power from the motor and thereby reduce costs? — JH, Australia
Find out the answer »

wind I'm studying how wind power is used to produce electricity and would like to know how a generator works. - MO, Canandaigua, New York
Find out the answer »

beam An electron beam, such as the one found in a TV picture tube, is composed of negatively charged electrons. Why is it that this beam does not rapidly spread out owing to the electric repulsion? I realize that the tube has various focusing magnets and such, but I would think the electronic repulsion would be a serious problem. - JT, Buffalo Grove, IL
Find out the answer »