ELECTRICAL CIRCUITS

What is this a picture of? - +

What is electric current? Electric Current (I) - a flow of electrons from the (+) terminal to the (-) terminal of a cell/battery through wires and components - +

Open and Closed Circuits Open circuit = switch is open = no current is flowing = bulb does not light Closed circuit = switch is closed = current is flowing = bulb lights up

Circuit Diagram & Symbols Cell/Battery Resistor Light Bulb Light Bulb Resistor Wires Switch

Types of Circuits Series Circuits – current takes only one path and is the same at each point. (One Wire connects ALL)

Series Circuits If one bulb blows out, it breaks the circuit and all the bulbs go out If you add more cells/batteries to a series circuit, the bulbs burn brighter

Types of Circuits Parallel Circuits – current takes more than one path and is NOT the same at each point. (Multiple Wires)

Parallel Circuits If one bulb blows out, there is still another complete circuit for the other bulb to stay lit

Draw these circuits in your Notebook Draw these circuits in your Notebook. Label each one as either Series or Parallel. A – Parallel B – Series

As a Quick Write in your notebook Compare and contrast conductors and insulators, give examples as well. Discuss with your elbow partner.

Conductor or Insulator?

Brighter or Dimmer? Dimmer

Series or Parallel? Series

Brighter or Dimmer? Brighter

Series or Parallel? Parallel

Series or Parallel? Series

Series or Parallel? Parallel

Ohm’s Law

Ohm’s Law

The Resistance is halved! What Happens? What happens to the Resistance when the Current is doubled and the Voltage stays the same? The Resistance is halved!

The Voltage is Tripled too! What Happens? What will happen to the Voltage when the Resistance is tripled and the Current remains constant? The Voltage is Tripled too!

What Happens? What happens to the Current when the Resistance is reduced by 1/3 and the Voltage stays the same? The Current is Tripled!

Measuring Current Current is measured in units of amperes or amps (A) In a series circuit, current is the same at all the points In a parallel circuit, current is shared between all the points

What is the current? SERIES CIRCUIT PARALLEL CIRCUIT 3A 3A 4A 1A 4A 1A

Measuring Voltage Voltage – the electrical push that a cell/battery gives to the current Voltage is also known as Potential Difference Voltage is measured in units of volts (V)

Measuring Voltage 3V 1.5V 3V In a series circuit, voltage is shared between all the points In a parallel circuit, voltage is the same at all the points

What is the current and voltage? Series Same Shared Parallel

What is the current and voltage?

In a series circuit, add up all resistance to get total. Measuring Resistance Resistance – slows down current, adding components to a circuit increases resistance Resistance is measured in units of ohms (Ω) More resistance = Less current = Less light In a series circuit, add up all resistance to get total.

Electrical Power

How much voltage gives 5 amps of current through a 3 Ω light bulb? I = V/R V = (5A)  (3Ω) V = 15V

How much current flows in a circuit with a 1 How much current flows in a circuit with a 1.5 volt battery and three 1 ohm resistances (bulbs) in series? I = V/R I = (1.5V) / (3Ω) I = .5A

What is the voltage drop across each resistor in the circuit? In a series circuit, voltage is shared between all the points 9V/3 = 3V

P = IV I = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A)  (1.5V) = 1.5 W A light bulb with a resistance of 1.5Ω is connected to a 1.5V battery in the circuit. Calculate the power used by the light bulb? P = IV I = V/R I = (1.5V) / (1.5Ω) I = 1A P = (1A)  (1.5V) = 1.5 W P = 1.5 W