The Basic lessons · Basic electronics and theory · B-005-006

Power and Heat: Managing Resistors Safely

Learn why resistor size matters for heat and how to calculate power in watts using voltage and current. Discover how to combine resistors to handle more power safely.

This lesson is part of SignalPrep Pro. The subsection's 11 exam questions are free to practise: practise B-005-006.

What this subsection asks

• Why would a large size resistor be used instead of a smaller one of the same resistance?
• A load requires 12 volts DC at 5 amperes. What is the minimum required power transformer rating?
• What is the DC input power of a transmitter operating at 12 volts and drawing 500 milliamperes?
• When two 500-ohm 1-watt resistors are connected in series, the maximum total power that can be dissipated by the resistors is:
• When two 500-ohm 1-watt resistors are connected in parallel, they can dissipate a maximum total power of:
• If the voltage applied to two resistors in series is doubled, how much will the total power change?
• Which of these combinations of resistors could make up a 50-ohm dummy load capable of safely dissipating 5 watts?
• How much current is drawn by a 12-volt, 30-watt light bulb?
• What is the power consumption of two 10-ohm resistors connected in series with a 10-volt battery?
• What is the advantage of replacing a 50-ohm resistor with a parallel combination of two 100-ohm resistors of the same power rating?
• Resistor wattage ratings are: