ELECTRON FLOW, RESISTANCE, and OHM’S LAW

Electron Flow vs Conventional Current(Read Page 440)

There are two ways to explain the way current moves:

______was the first system used to explain electron flow (some electricians still use this)

______is the newer system used to explain electron flow

Both systems are used today

Conventional Current:____________

Electron Flow:______

Resistance: (Read Pgs 441-442)

Resistance:______

______

All substances resist electron flow to some extent

______, like metals, have low resistance

______have high resistance

Resistance is measured in ______ (Ω)

Give an example of a load” ______.

A load adds resistance to a circuit. It gains energy from the electrons that pass through it. For this reason, they can get ______.

A load can act as a resistor. However, small resistors are added to a circuit to help reduce the ______.

Explain how the smaller pipe in Fig 11.21 is similar to how resistors affect the flow of electrons. ______.

______.

What does resistance do?

Why do you think resistors are used in a circuit? ______

______.

What does increasing resistance do to a circuit? ______

______.

What does decreasing resistance do to a circuit? ______

______.

Since increasing resistance reduces current, potential difference (voltage) increases. Look at the diagram of the water pipe and explain why. ______

______.

Factors That Affect Resistance (Read Pg 443)

1: / Metals that are good conductors that decrease resistance. Silver is the most conductive metal, therefore it has the least resistance.
2: / As temperature increases, conductivity decreases. Therefore, the hotter the wire, the higher the resistance.
3: / The longer the wire, the higher the resistance. Therefore, if the length of a wire is doubled, the resistance is doubled.
4: / Thick wires conduct more electricity than thin wires. Therefore, the thinner the wire, the higher the resistance.

Georg Ohm(Read Pgs 458-459)

A German man who studied mathematics and then electricity

He devoted much of his life to the study of potential difference, current and resistance.

His discoveries have led us know much of what we understand today about electricity.

What is Ohm’s Law:(Read Pg 460)

Remember:Remember a “Law” in Science is a conclusion after a great number of experiments and much collection of evidence. It is accepted by the whole science community.
Ohm’s Law: VIR Triangle
  • The V I R triangle can be used to calculate all formulations of Ohm's law.
  • Use a finger to hide the value to be calculated. The other two values then show how to do the calculation.

Voltage (Potential Difference):

Measured in: ______

Current:

Measured in: ______

Resistance:

Measured in: ______

Complete VIR problems 11.1-11.3 on pp. 460-461 on a separate sheet of paper. 9 Problems in total.

Homework

Complete the Practice Problems on the handout. Use GRASP.

Complete questions p. 447 #8, 9, 10, 13