# Ohm’s Law Foundations of Technology Ohm’s Law © 2013 International Technology and Engineering Educators Association, STEM Center for Teaching and Learning™

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Foundations of Technology

Ohms Law 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology Teacher Resource Unit 4 Lesson 4

STEMCenter for Teaching and Learning

The BIG IdeaBig Idea:

Troubleshooting allows users to continue to use and maintain the proper operation of a system or product.

2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Proposed by George Ohm, and is the relationship between Voltage, Current and Resistance.

Voltage (V) = Current (I) X Resistance (R)

Ohms Law 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Ohms Law is commonly expressed using the triangle found below where:

Voltage (V) = Current (I) X Resistance (R)

Current (I) = _Voltage (V)__ Resistance (R)

Resistance (R) = _Voltage (V)_ Current (I)

Ohms Law 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Voltage (V) is the electrical force that moves electrons through a conductor.

Voltage is electrical pressure that pushes electrons.

Voltage 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Current (I) is the quantity or flow rate of electrons moving past a point.

Current flow is also known as amperage, or amps for short.

Current 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Resistance (R) is the force that reduces or stops the flow of electrons and opposes voltage.

Resistance 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Using Ohms Law determine the missing value for the following circuit:

Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

4.50.5 Amp= ______

Using Ohms Law determine the missing value for the following circuit:

Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

4.50.5 Amp= ______Resistance (R) = Voltage (V) Current (I) R = 4.5V 0.5Amp

R = 9

Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

10 0.5 Amp_____I = ______ Amp

10 0.5 Amp_____I = ______ Amp I = 0.5 Amp - Current will be the same throughout the circuit

Voltage (V) = Current (I) x Resistance (R) V = 0.5 Amp x 10

V = 5V

In a Series circuit, the current through two or more resistors is the same, and the circuit is connected in a series.

The total resistance of the collection is the sum of individual resistances.

Resistors in Series 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

The total resistance of the collection is the sum of the individual resistances.

The Equivalent Resistance of R1, R2 and R3 when connected in series is:

R = R1 + R2 + R3

Resistors in Series 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Calculate the total resistance of the series circuit:

-+VI95 10 3

Calculate the total resistance of the series circuit:

-+VI95 10 3 R = R1 + R2 + R3

R = 3 + 10 + 5

R = 18

Calculate the total current of the series circuit: (current is the same throughout a series circuit)

-+VI95 10 3 R(total) = 18

Calculate the total current of the series circuit: (current is the same throughout a series circuit)

-+VI95 10 3 R(total) = 18

Current (I) = Voltage (V) Resistance (R) I = 9V 18 I = 0.5 Amp

Using Ohms Law, calculate the voltage drop for each resistor in the series circuit:

-+VI95 10 3 0.5 Amp

Using Ohms Law, calculate the voltage drop for each resistor in the series circuit:

-+VI95 10 3 V = I x R

V(R1) = 0.5 Amp x 3 V(R1) = 1.5 V

V(R2) = 0.5 Amp x 10 V(R2) = 5 V

V(R3) = 0.5 Amp x 5 V(R3) = 2.5 V

0.5 Amp

Using Ohms Law, calculate the voltage drop for each resistor in the series circuit:

-+VI95 10 3 Remember Current (I) is the same across a series circuit.0.5 Amp

R1R2R3Total1.552.59 VVoltage0.50.50.50.5 AmpCurrent310518 Resistance

In a Parallel circuit, the voltage through two or more resistors is the same, and the circuit is connected in parallel.

The total resistance of the collection is divided among the three resistors .

Resistors in Parallel 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

The total resistance of the collection is divided among the three resistors.

The Equivalent Resistance of R1, R2 and R3 when connected in parallel is: 1/R = 1/R1 + 1/R2 + 1/R3

Resistors in Parallel 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

Calculate the total resistance of the parallel circuit:

I

Calculate the total resistance of the parallel circuit:Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

1/R = 1/R1 + 1/R2 + 1/R3

1/R = 1/(10 ) + 1/(2 ) + 1/(1 )

1/R = 0.1 + 0.5 + 1

1/R = 1.6

R = 1/(1.6 ) R = 0.625 I

Calculate the total voltage of the parallel circuit: (voltage is the same across a parallel circuit)Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

R(total) = 0.625

I

Calculate the total voltage of the parallel circuit:Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

R(total) = 0.625

Voltage (V) = Current (I) x Resistance (R) V = 14.4 Amp x 0.625 V = 9V

Calculate the total voltage of the parallel circuit: (voltage is the same across a parallel circuit)I

Using Ohms Law, calculate the current across each resistor in the parallel circuit:Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

-+VI910 1 2 14.4 Amp

Using Ohms Law, calculate the current across each resistor in the parallel circuit:Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

-+VI910 1 2 Current (I) = Voltage (V) Resistance (R)

I(R1) = 9V 10

I(R1) = 0.9 Amp 14.4 Amp

Using Ohms Law, calculate the current across each resistor in the parallel circuit:Practice Questions 2013 International Technology and Engineering Educators Association, STEMCenter for Teaching and Learning Foundations of Technology

-+VI910 1 2 Current (I) = Voltage (V) Resistance (R)

I(R2) = 9V 2

I(R2) = 4.5 Amp 14.4 Amp

-VCurrent (I) = Voltage (V) Resistance (R)

I(R3) = 9V 1

I(R3) = 9 Amp

Using Ohms Law, calculate the current across each resistor in the parallel circuit:

Remember Voltage (V) is the same across a parallel circuit.V

R1R2R3Total9999 VVoltage0.94.5914.4 AmpCurrent1021 0.625 Resistance

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