Physics 1bl Electric Potentials And Fields (Page 3 of 6) in pdf

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Physics 1BL

Electric Potentials & Fields

Summer Session II 2010

one end and alligator clips on the other. Fasten the red clip to one metal pushpin and

the black one to the other.

A4. Plug the rounded (banana) end of the red wire into the positive (+) terminal on the

power supply, and the black wire into the negative (-) terminal. This provides a

potential difference across the electrodes. We could use a battery in place of the power

supply, just as you could choose to run any electrical appliance with a battery. But

using electrical energy from the power grid from SDGE is usually cheaper and easier

than using batteries. It also allows us to vary the potential we want just by turning a

knob. Set the voltage from the power supply to 10 V. Whenever you connect a power

supply or large battery to a circuit, you should make sure there is some sort of

resistance between the positive and negative terminals. If you create a path without

any resistance between the two terminals (e.g. connecting the terminals with only a

piece of wire or other conductor) you will create what is called a "short circuit" and

the high currents that will flow through this circuit can cause injury and damage

equipment.

A5. The Teledeltos paper does not conduct charges very well. In comparison, the silver

ink used to draw the diagram on the Teledeltos paper is a good conductor of charge.

When the power supply is turned on, charge builds up on the conductors drawn with

the silver ink. What path do charges follow between the silver ink conductors?

A6. You now have the power supply providing the potential difference across the two

conductors. Next, you want to be able to measure the voltage at any position on the

teledeltos paper. Connect the negative terminal of the multimeter to the silver

electrode that is already connected to the negative terminal of the power supply, as

shown in the diagram. The positive terminal of the multimeter is now your “probe”

and will measure the potential at any point with reference to the common “ground”

which is the negative of the power supply.

Physics 1bl Electric Potentials And Fields Page 3