54 Activities
Calculating Electrical Terms
- The statement which correctly represents Ohm’s law:
a. V = IR
b. V = R/I
c. R = VI
d. I = R/V - A 10-ohms resistor is powered by a 5-V battery. The current flowing through the source is:
a. 10 A
b. 50 A
c. 2 A
d. 0.5 A - If V = 50 V and I = 5 A, then R = ?
a. 50 Ω
b. 5 Ω
c. 10 Ω
d. 2 Ω - If P = 50 watt and R = 2 ohms, then I = ?
a. 50 A
b. 5 A
c. 10 A
d. 2 A - Unit of voltage is:
a. Volt
b. Watt
c. Coulomb
d. Ampere - Unit of current is:
a. Volt
b. Watt
c. Coulomb
d. Ampere - Unit of power is:
a. Volt
b. Watt
c. Coulomb
d. Ampere - Unit of resistance is:
a. Volt
b. Watt
c. Ohms
d. Ampere - If I = 5 A and R = 10 Ω, then P = ?
a. 50 watts
b. 250 watts
c. 350 watts
d. 500 watts
Watt’s Law (Power) problems:
- P = 10 watts, I = 2 amperes, then E = __________ V
- E = 100 volts, I = 0.5 amps, then P = __________ W
- P = 500 watts, E = 250 V, then I = __________ A
Answers
- V = IR
- 2 A
Solution: From I = V/R = 5-V/10 ohm = 0.5 A - 10 Ω
Solution: From R = V/I = 50 V/ 5A = 10 Ω - 5 A
Solution: From I = √(P/R) = √(50 V/ 2A) = √25 A = 5 A - Volt
- Ampere
- Watt
- Ohms
- 250 watt
Solution: Here P = I2R = (5 A)2 * 10 Ω = 250 watts - 5V
Solution: Here 10W/2A = 5V - 50W
Solution: Here 100V × .5A = 50W - 2A
Solution: Here 500W/250V = 2A
Practical Competency “Use Multi Meters”
Never measure Resistance and use the Ohmeter function on a live circuit.
Objective
To complete this Practical Competency you will be expected to use a Various Analogue meters, a Digital Multimeter (DMM) and a Clamp-on Ammeter. Meters are used daily in the field for safety testing and troubleshooting purposes. Using them correctly and safely is vital. The purposes of this Practical Competency are:
- To safely use various meters to measure Voltage, Current and Resistance
- To correctly use different types of meters (Analog and Digital)
- To demonstrate the affect of increasing resistance in an electrical circuit
Safety
- Students must have steel toe boots, appropriate clothing, and safety glasses for use in the labs
- Students must perform a Hazard assessment of the work area.
- Never use the Ohmmeter function on a live circuit
- If you are unsure about using a Meter or piece of equipment, consult the user manual.
Equipment and materials
- Elworthy Bench (Electrical Bay #1)
- Digital Multimeter and Clamp-on Ammeter (Tool Crib)
- Assortment of Test Leads (Tool Crib)
Using Ohm’s and Watt’s Law, calculate the expected circuit values and record in Table 1
*Only measure resistance when circuit is de-energized!
- Calculate values first.
- Obtain the material listed above, from the Tool crib and choose an Elworthy bench that is not in use.
- Measure the 50, 100 and 150 Ω Resistors to confirm their values and ensure that they are functioning and record your measurements in Table 2 before connecting in the circuit below.
- Connect the Circuit shown below, using the variable DC power supply and starting with the 50 Ω Resistor. Connect the analogue meters sup