Ohm's Law

Ohm's Law

Objectives

• Discuss the relationship of current to voltage and resistance in an electric circuit

• Solve problems involving Ohm’s Law

Poll

Voltage is a power source that causes electrons to move to generate current.

• true

• false

Poll

Loads like bulbs affect the movement of electrons.

• true

• false

Poll

Negatively charged particles can easily flow in an insulator.

• true

• false

Poll

There will be current even wires are cut.

• true

• false

Poll

Static electricity occurs if two objects in contact have no charge.

• true

• false

Open Ended

what is the main role of voltage in circuitry?

Open Ended

What is the main role of resistance in a circuitry?

Open Ended

What is the effect on electric current in a simple circuit if the voltage is high or low?

Activity 1 Virtual DC Circuit Building

MATERIALS: 2 small bulb,3 thin wire, 2 batteries ( 1.5 volts battery and 3 volts battery) and small electrical tape.

PROCEDURE:

First Set-Up

1.   Connect 2 thin wires at both ends of a 1.5v battery.

2.   Screw the end of thin wires to bulb.

3.   Repeat step 1-2, this time use the 3 volt battery

4.   After observing, disconnect the materials.

Second Set-Up

1.   Connect thin wires at both ends of 3v battery.

2.   Attach the bulb to end of the wires (1 bulb to left and another 1 to the right)

3.   Connect the two bulb using the last piece of wire you have.

4.   Observe the brightness of the two bulbs.

5.   Remove one wire, one bulb and one holder in the set-up then connect what remains in the set-up. Compare the brightness of one bulb to two bulbs connected lately.

Open Ended

In the first set-up, which battery causes the bulb to light brighter? Why?

Open Ended

1. How is voltage of a battery affect the brightness of a bulb?

Open Ended

1. In the second set-up, how will you compare the brightness of a two-bulb circuit from a one-bulb circuit?

Open Ended

1. What is the relationship between the number of bulbs and brightness in a circuit?

OHM'S LAW

• Law that portrays the relationships between current (I), Voltage (v) and Resistance (Ώ). 

• The law was named after its proponent George Simon Ohm (1789-1854).

• A simple formula is used to show the relationship of current, resistance and voltage.

  ΔV = I • R

• The electric potential difference between two points on a circuit (ΔV) is equivalent to the product of the current between those two points (I) and the total resistance of all electrical devices present between those two points (R). 

Open Ended

A motor with an operating resistance of 45 is connected to a voltage source. The current in the circuit is 4.88 A. What is the voltage of the source?

Open Ended

Determine the amount of current going through a 100 Ω; resistor with a voltage of 120 V.

Open Ended

A small light bulb is connected to a 9 V battery and draws 2.5 A of current. What is the net resistance of the bulb?