The document explains Ohm's Law, discovered by Georg Simon Ohm in 1816, which describes the relationship between voltage, current, and resistance in a circuit. It states that current is directly proportional to voltage and inversely proportional to resistance, with linear relationships demonstrated through calculations and graphs. The document also includes examples for calculating current and voltage under different resistance conditions.

1. Contents
1
1. Ohm’s Law
2. Relationship of Voltage, Current,
Resistance
3. Calculating Voltage, Current,
Resistance

2. Introduction
 In 1816 Georg Simon Ohm found that
current, voltage, and resistance are related
in a specific and predictable way.
 Ohm expressed this relationship with a
formula that is known today as Ohm's Law
• Ohm's law describes mathematically how
voltage, current, and resistance in a circuit
are related.
2

3. 3
•Ohm determined experimentally that if the voltage
across a resistor is increased, the current through the
resistor will also increase; and, likewise, if the voltage
is decreased, the current will decrease.

4. 4
Ohm also determined that if the voltage is
kept constant, less resistance results in more
current, and, also, more resistance results in
less current.

5. 5
Ohm's law states that current is directly
proportional to voltage and inversely
proportional to resistance.

6. 6

7. The Linear Relationship of Current
and Voltage:
 In resistive circuits, current and voltage are
linearly proportional.
 Linear means that if one of the quantities is
increased or decreased by a certain
percentage, the other will increase or
decrease by the same percentage, assuming
that the resistance is constant in value.
 For example, if the voltage across a resistor
is tripled, the current will triple.
7

8. 8

9. 9
Let's take a constant value of resistance, for
example, 10.0, and calculate the current for
several values of voltage ranging from 10 V to
100 V in the circuit in Figure.
The current values obtained are shown in
Figure. The graph of the I values versus the V
values is shown in Figure. Note that it is a
straight line graph. This graph tells us that a
change in voltage results in a linearly
proportional change in current.

10. 10

11. 11
As you have seen, current varies inversely with
resistance as expressed by Ohm's law, I = VR. When
the resistance is reduced, the current goes up; when
the resistance is increased, the current goes down.
Let's take a constant value of voltage, for example,
10 V, and calculate the current for several values of
resistance ranging from 10 n to 100 n in the circuit
in Figure. The values obtained are shown in Figure.
The graph of the I values versus the R values is
shown in Figure.
The Inverse Relationship of Current and
Resistance

12. 12

13. 13
Calculating Current:
Solution:

14. 1. If the resistance is 47 ohm and the voltage is 50
volt, what is the current?
2. If V= 5 V and R=1000 ohm, what is the current?
3. If V= 50 V and R=1 K ohm, what is the current?
4. If V= 50 V and R=10 K ohm, what is the current?
14
Related Problems:

15. 15

16. 16
1. If V= 25 V and R=1.8 M ohm, what is the
current?
2. If R is doubled in the circuit, what is the
new value of current?

17. 17

18. Calculating Voltage
18

19. 19

20. 20

21. 21

22. 22