IB Physics 12 Mr. Jean November 4 th, 2013

The plan: Video clip of the day Circuit diagrams Circuit symbols How to draw circuits

Electric Circuits: To draw out each individual component would be quite time consuming; therefore the world of circuits essentially have their own language to indicate what these symbols are.

Electric Circuits: Like notation in physics, this is not one agreed upon universal set of symbols which are used for every drawing; however here is the system we’ll use to create circuits in IB.

Understanding Circuit Diagrams:

Important to Note: Remember that by definition “Current” is the flowing from positive to negative potential. Current uses the conventional flow which is a bit unfortunate because electron flow is from the negative terminal to positive terminal.

Important to Remember: Conventional Flow talks about the “direction of the current” which is the OPPOSITE direction of the electron flow.

Key points to circuit diagram: Circuit diagrams show the connections as clearly as possible with all wires drawn neatly as straight lines. The actual layout of the components is usually quite different from the circuit diagram and this can be confusing. The secret is to concentrate on the connections, not the actual positions of components.

Purpose: A circuit diagram is useful when testing a circuit and for understanding how it works. This is similar to a force diagram for understanding dynamics.

Additional Useful Keys for Success: Make sure you use the correct symbol for each component. Draw connecting wires as straight lines. Put a 'blob' ( ) at each junction between wires. Label components such as resistors and capacitors with their values listed along side or below the circuit. The positive (+) supply should be at the top and the negative (-) supply at the bottom.

This is an example of a light and how it works in a circuit.

How to draw circuits: 1)Start at the source of potential energy. 2)Draw the circuit from positive (+) terminal to negative (-). 3)Electric Current (I) travels from negative terminal to the positive. 4)Label component in the order in which they appear dictated by the electric current (I)

How to draw circuits:

Create the following circuits: 1) Create a circuit that has a 9V battery with three resistors R 1, R 2, and R 3. 2) Create a circuit with an AC power supply, a resistors, a lamp, another resistor, a heater, and a push button switch. 3) Create a circuit with a battery as the power supply, a resistor, On / Off switch, a capacitor, a diode, and another resistor.

Problems: 1) Draw a circuit diagram with three resistors, a battery as a power source and one push button switch. 2) Draw a circuit diagram with 4 resistors, 1 capacitor, an alternating (AC) power supply, with an led dipole controlling electric flow in the clock wise direction.

Problems: 1) Draw a circuit diagram with three resistors, a battery as a power source and one push button switch. 2) Draw a circuit diagram with 4 resistors, 1 capacitor, an alternating (AC) power supply, with an led dipole controlling electric flow in the clock wise direction.

Exchange Diagrams Have your neighbour examine your diagram. –Questions to consider. Does the diagram includes all of the necessary pieces? Does the diagram clearly indicate what is going on? Could you use this diagram to create the circuit above given the components in a lab?

Example #1:

Example #2:

Return diagram to neighbour: To do: –Respond to the questions to consider 1) Give your neighbour constructive feedback and indication of how they are doing with their diagrams. 2) Think of ways their diagrams can be improved 3) Think of things which you will take from their diagram to improve your future drawings.