Instruction Manual peqPOWER 250 Volt Power Supply
OPERATIONAL ELECTRICAL PARAMETERS
Power Considerations
Electrophoresis is the migration of a charged particle under the influence of an electrical field. The
power supply output parameters voltage, current and power are related by the following two equations:
Voltage (V) = Current (I) x Resistance (R); (V=I*R)
Power (P) = Current (I) x Voltage (V); (P=I*V)
Resistance
Resistance of the assembled electrophoresis cell is dependent on the conductivity of the gel buffer, the
thickness of the gel, and the number of gels being run. Although the resistance is determined by the gel
system, the resistance can vary over the course of an electrophoretic separation. For instance, in the
Tris-Glycine buffer system, the fast moving, highly conductive chloride ions in the gel are gradually re-
placed by the slower moving, less conductive glycine ions from the running buffer as the gel runs. As a
result, the resistance of the gel increases as the chloride/glycine front moves down the gel, and the cur-
rent decreases.
Voltage
The velocity with which an ion moves in an electric field will vary in proportion to the field strength (volts
per unit distance). The higher the voltage the faster an ion will move.
Current
Current is a function of the number of ions passing a given cross-section of the circuit at a given time.
For a given gel/buffer system, at a given temperature, current will vary in proportion to the field
strength (voltage) and/or cross-sectional area (number and/or thickness of the gels). Ions in solution
and at a given voltage will move faster as the temperature increases, increasing current.
Power
The power in Watts, or the rate of heat generated by the system, is directly proportional to voltage and
current (P=I*V).
COMMON ERRORS FOUND WITH ELECTROPHORESIS POWER SUPPLIES
No load
The electrophoresis system is not connected to the power leads, check the power leads
The electrophoresis system has a short, the Pt wire is broken or the banana connectors are dam-
aged
Buffer concentration too low
Buffer volume too low
Short in power cord
Current has dropped below acceptable rating (10 mA)
PEQLAB_v0412E
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