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Name: _______________________ Student #: ____________________ Lab Group: ___________________

Mark /10: _______________________

1002pes Biophysics, Semester 2, 2013

Notations: _______________________ Notations: _______________________

Laboratory 3 ELECTRICAL CIRCUITS AIMS The aims of this laboratory are to:

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Investigate the validity of Ohm's law in a DC circuit Examine Kirchhoff’s laws for series and parallel DC circuits Become familiar with the use of a digital multimeter

EQUIPMENT

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DC power supply Digital Multimeter (DMM) Resistors: 330 Ω, 1 kΩ, 2.2 kΩ, 4.7 kΩ Resistance colour chart Protoboard and leads Alcohol wipes

INTRODUCTION Direct current (DC) electrical circuits carry electrical current in one direction, and are used within a wide range of clinical situations such as EMG amplification and computerized instrumentation experiments. Regardless of the overall complexity of a DC circuit, the circuit is always governed by the simple laws investigated in this laboratory: Ohm's law Ohm's law states that the potential difference, V, between the ends of a conductor is directly proportional to the current, I, flowing through that conductor: V = IR, where R is electrical resistance with units of ohms (Ω). Ohm's law is not applicable to all conducting media, but is valid for a wide range of conducting materials, including metals.

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1002pes Biophysics, Semester 2, 2013

Resistors are denoted in circuit diagrams by the symbols:

for a fixed resistor, and

for variable resistors.

A resistor’s value is given by colour-coded bands on its packaging case. The effective (total) resistance of two resistors connected in series and in parallel is given below:

series:

Reff = R1 +R2

parallel:

Reff =

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1002pes Biophysics, Semester 2, 2013

Kirchhoff's rules Junction rule: The total current entering a circuit junction must equal the total current leaving that junction, since electric current is always...