LAB 9 CIRCUITS

In a series circuit, the same current goes through each resistor, therefore the effective resistance is the sum of the individual resistances. In a parallel circuit, the same voltage drop is across each resistor, therefore the effective resistance is the reciprocal of the sum of the reciprocals of each resistor. In circuits where the resistors are connected in parallel and series combinations, the circuit can be analytically simplified in order to calculate the effective resistance

Voltage drops and currents in various parts of the circuit can be calculated using the Ohm's Law. Voltage drop around a loop should always be zero and curents flowing into a node should be equal to the current flowing out of a node

Purpose:

Verify individual and total resisitance, voltage drop and current in simple circuits.

Observe diodes and their properties.

Combine resistors and batteries to form simple circuits.

MATERIALS:

Electronics circuit breadboard, resistors, wires, multimeter

DIAGRAM

PROCEDURE:

REMEMBER TO TURN THE SWITCH OFF AFTER EACH MEASUREMENT FOR CURRENT OR VOLTAGE DROP.

PART A

1. Create a simple circuit using a voltage source ( battery), a switch and an L.E.D. Notice the level of brightness of the light. Try reversing the polarity (switch the positive with the negative end of the L.E.D. What do you notice?
2. Measure the voltage across the battery terminals.
3. Measure the resistance of the 470 W, 1000 W, and the 4700 W resistors.

voltage	470 W resistor	1000 W resistor	4700 W resistor

1. Connect a simple circuit using a switch, a voltage source and a 1000W resistor.. Measure the voltage across the resistor and the current through it.
2. Voltage across resistor: ____________
3. Current through resistor: ____________

 

PART C

4. Connect a simple circuit using a switch, a voltage source and a 1000 W resistor in series with a 470 W resistor. Measure the voltage across each resistor and the current through each resistor.

	Voltage across	Current through
1000 W resistor
470 W resistor

 

PART D

5. Connect a simple circuit using a switch, a voltage source and a 1000 W resistor in parallel with a 470 W resistor. Measure the voltage across each resistor and the current through each one. Also measure the current out of the battery.

	Voltage across	Current through
1000 W resistor
470 W resistor
battery	XXXXXXXXXXXXX

 

PART E for AP Physics only

 Connect a circuit as shown on the right above. Measure the voltage across each resistor and the current through each one. Also measure the current out of the battery.

	Voltage across	Current through
1000 W resistor
470 W resistor
4700 W resistor
battery	XXXXXXXXXXXXX

6. Disconnect all wires and take out the batteries after checking to make sure you have all the data required.

CALCULATIONS:

1. Calculate the expected current through and the expected voltage across each resistor using the Ohm's Law. Use the measured voltage for the battery and the measured resistances.
2. Find the percent difference for each measured value based on the calculated value.

ANALYSIS:

1. What happens when the polarity is switched on the L.E.D.? Explain.
2. Discuss the measurements for part C and compare with that of part D.
3. How do the measured values for voltage and current compare with the expected values?

CONCLUSION: