Practical Ohm\'s Law PDF

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Summary

Procedure on a practical about Ohm's Law and experiemental results....

Description

Practical Ohm’s Law Outcomes ● investigate quantitatively the current–voltage relationships in ohmic and non-ohmic resistors to explore the usefulness and limitations of Ohm’s Law using: – � = �� – � = �� (ACSPH003, ACSPH041, ACSPH043) ● investigate quantitatively and analyse the rate of conversion of electrical energy in components of electric circuits, including the production of heat and light, by applying � = �� and � = �� and variations that involve Ohm’s Law (ACSPH042) ● investigate quantitatively the application of the law of conservation of energy to the heating efects of electric currents, including the application of � = �� and variations of this involving Ohm’s Law (ACSPH043) Aim To find how voltage and current change in a circuit with a resistor? Risk Assessment Identify Trip hazard

Rating Medium

Electric shock Electric shock (2)

Low Low

Minimisation Tightly wrap cable around transformer with no excess cable hanging around Use 2-12V Start with low volts on transformer to avoid short circuit

Procedure 1) Set up the equipment below

2) Connect the negative terminal of the transformer to the negative terminal on the ammeter 3) Connect the positive terminal of the ammeter to the right side (negative terminal) of the resistor set

4) Connect the positive terminal of the resistor set to the negative terminal of the second ammeter 5) Connect the positive terminal of the second ammeter to the positive DC terminal 6) Connect the negative terminal of the resistor set to the negative side of the voltmeter 7) Connect the positive terminal of the resistor set to the positive side of the voltmeter 8) Turn the transformer to 2 volts and turn the switch on 9) Record the results of the first and second ammeter and voltmeter 10) Repeat this process by changing the volts of the transformer up by 2 11) Take the banana clips from the 5Ω resistor to 100Ω 12) Record the results of the first and second ammeter and voltmeter Table of Results Resistor

Transformer setting (V)

R=

V I 50Ω

100Ω

200Ω

A₁ V A₂ A₁ V A₂ A₁ V A₂

2 0.04 2.34 0.04 0.01 2.40 0.02 0.01 2.45 0.01

4 0.07 4.20 0.08 0.03 4.27 0.04 0.01 4.34 0.02

6 0.11 6.30 0.12 0.05 6.40 0.06 0.02 6.44 0.03

8 0.16 8.40 0.21 0.07 8.50 0.08 0.03 8.57 0.04

10 0.20 10.64 0.21 0.10 10.80 0.10 0.04 10.89 0.05

12 0.25 12.96 0.25 0.12 13.20 0.13 0.05 13.29 0.06

52.1

113.06

243

Analysis 1) Find the resistance of the resistor set 50Ω, 100Ω and 200Ω. Fill out the V/I column and calculate the average resistance in ohms (Ω) in your results table. 2) Draw a graph of V vs I. Find the gradient of the graph for the 50Ω, 100Ω and 200Ω resisters. Compare the gradient with the V/I column in your results table. Comment on:

50Ω V vs I 14 12

100Ω V vs I

10

14

8

12

6

10

4

8

2

6

0

0

4

Current (A)

2 0

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

200Ω V vs I 14 12 10

Volt age (V)

8 6 4 2 0

0

0.01

0.02

Current (A)

0.04

0.05

0.06

a) What does the gradient represent in a graph of V vs I. Find the gradient for each resistor 50Ω, 100Ω and 200Ω.

b) Are the gradients for 50Ω, 100Ω and 200Ω similar to the V/I column result. Should they be diferent? Explain why or why not. The gradients of the resistors and the V/I column result should be similar as they are both calculating the resistance. c) Which of the graphs are ohmic? Discuss. All three are ohmic as they all obey Ohm’s law, that is resistance being constant for the values of current or voltage. Furthermore, this is proven through the graph of the values of Voltage over Current which is found in the formula R = V/I and the graph being linear. 3) Why did we use two ammeters? What comment can you make about the reading on both ammeters? Explain. We used two ammeters in this experiment to identify the current on both sides of the resistor. The readings on both the ammeters were very close however only equal sometimes. Although they should be the same, due to the resistance in each of the ammeters not being the exact same, it has resulted in slight variations.

Conclusion Ohm’s Law states that voltage is proportional to current multiplied with resistance, giving the formula of V = IR. Ohm’s law shows a linear relationship between the voltage and current in an electrical circuit. The conversion of electrical energy within this experiment involving Ohm’s law was identified through using a 50Ω, 100Ω and 200Ω resistor. From the results table, we can examine that as the resistance increases, the voltage within the circuit also increases. In addition, as the resistance increases, the current within the circuit decreases.

Extension The current-voltage relationship in Ohmic resistors follow Ohm’s Law which is when resistance is equal to voltage divided by the current (have a constant resistance). An application of an ohmic resistor is where a standard resistor is required in a circuit. For instance, when requiring a certain value of amps an ohmic resistor would be placed. When applying diferent voltages and measuring current, a graph of the voltage vs current would be linear if plotted and would also represent the resistance. They are used in scenarios in which a linear relationship between voltage and current is expected, e.g. in amplifiers, filters, oscillators and clampers. Ohmic resistors are placed like normal components and are used to limit current, divide voltage, select frequency and bypass current.

The current-relationship in non-Ohmic resistors do not obey Ohm’s Law, where the resistance is not constant and depends on a way that depends on the voltage across it. When the graph of voltage vs current is plotted for a non-ohmic resistor, the line does not come out to be linear, but has a curved shape. Examples of non-ohmic resistors include of tungsten filament, diode and a thermistor. These resistors do not have constant resistance as when voltage increases, the electrons transfer more energy to the atoms of the conductor leading to greater vibrations, and in temperature and resistance. Uses of Ohm’s Law includes of in voltage divider circuits where source voltage is divided across the output resistance, in electric circuits where intentional voltage drops are required to supply specific voltages to diferent elements and in DC measuring instruments to divert current. Limitations include

of the inability of the law to be placed in unilateral networks which have diferent voltage-current relationships and for non-linear elements.

References Web Address

Website name

http://www.diferencebetween.net/technology/diference -between-ohmic-and-non-ohmic-conductors/

Diference between ohmic and non-ohmic conductor s What is an Ohmic Resistor? Ohm’s Law

https://www.techwalla.com/articles/what-is-an-ohmicresistor https://www.electrical4u.com/ohms-law-equationformula-and-limitation-of-ohms-law/

Organisatio n responsible for web site Diference between.ne t

Date Accesse d 14/8/19

Techwalla

14/8/19

Electrical 4 U

14/8/19...