## Current and Resistance

 What is electric current? What is its unit? What do you mean by a conductor? an insulator? What types of materials are conductors? What causes an electric current (amperes) to flow in a wire? What are the analogies to voltage, current, and resistance in a closed water circuit? What physical factors determine the electrical resistance of a wire? How does the resistance of a wire change with temperature? What is Ohm's Law? How does the drift speed of electrons through a wire compare to the rate of travel of an electric signal? How is the electric power calculated in a DC circuit? What is a semiconductor? What is a superconductor? *Electric current *Current in wire *Conductors and insulators *Resistance *Voltage *Water circuit analogy *Resistivity *Temperature dependance *Ohm's law *Electron drift velocity *Power relationship *Semiconductor *Superconductor
Index
HyperPhysics***** Physics 1112K Go Back

## Direct Current Circuits

What causes an electric current (amperes) to flow in a wire?

What are the analogies to voltage, current, and resistance in a closed water circuit?

What is Ohm's Law?

What is the voltage law? Draw the analogy to the behavior of a water circuit.

What is the current law? Draw the analogy to the behavior of a water circuit.

How is the electric power calculated in a DC circuit?

How do you determine the equivalent resistance of two resistors in series? in parallel?

How do you determine voltages and currents for two resistors in series? in parallel?

How can you measure electric resistance with a voltmeter and ammeter?

What is meant by emf?

How do you calculate voltage and current in a circuit which has more than one loop?

Describe the charging of a capacitor by a battery.

What is meant by the time constant in capacitor charging?

Describe the discharge of a capacitor.

## Elements of practical electric circuits

Describe the basic layout of standard U.S. household wiring systems. Why are there two high voltage or "hot" wires?

Why are standard U.S. receptacles "polarized" with one wide prong and one narrow prong?

What is the function of a fuse or circuit breaker?

What is the function of a ground wire?

If the ground wire is broken, what indication of this will you get from the operation of the appliance?

Is household wiring in series or parallel? Why?

Why is it that a small amount of corrosion on an auto battery terminal can prevent the engine from starting?

If the auto won't start and you suspect the battery, are the headlights and horn operation a good test of the battery's strength?

Why is it that a battery may test at normal voltage even when it is too spent to supply appreciable power to a circuit?

What is meant by a "short circuit"? an "open circuit"?

*Voltage

*Electric current

*Resistance

*Water circuit analogy

*Ohm's law

*Voltage law

*Current law

*Power relationship

*Resistor combinations

*Series and parallel circuits

*Voltmeter-ammeter measurements

*Voltmeter

*Ammeter

*emf

*Two-loop circuit

*Capacitor charging

*Time constant

*Capacitor discharge

*Household wiring

*Polarized plugs

*Breakers and fuses

*Ground wire

*Appliance ground

*Series circuit

*Parallel circuit

*Auto battery example