Ohm’s Law Flashcards
(14 cards)
Name 3 ways DC can be generated.
- Batteries
- Solar Cells
- Dynamos
- Bridge Rectifiers
What is the conventional current flow in a circuit?
Positive to Negative.
Name four ‘rules’ that apply to DC, single pathway circuits.
- Ohm’s Law:
This states that the voltage (V) across a resistor is directly proportional to the current (I) flowing through it, and the proportionality constant is the resistance (R). Mathematically, this is expressed as V = I * R. - Kirchhoff’s Voltage Law (KVL):
The sum of voltage drops around any closed loop in a circuit must equal the source voltage (or zero if you consider the loop starting and ending at the same point). - Kirchhoff’s Current Law (KCL):
The sum of currents entering a junction (a point where multiple wires connect) must equal the sum of currents leaving the same junction. - . Resistance in Series:
In a single-pathway (series) circuit, the total resistance is the sum of the individual resistances.
Express Ohm’s Law in words and also in mathematical terms.
Ohm’s Law:
This states that the voltage (V) across a resistor is directly proportional to the current (I) flowing through it, and the proportionality constant is the resistance (R).
Mathematically, this is expressed as V = I * R
In your words, what would happen to the current in a circuit if the resistance was practically zero?
Extremely high current, or words that effect.
How is a resistance meter connected?
Circuit must be dead.
Connected parallel with the load.
If connected to a live circuit, damage to the meter is likely.
How is an insulation resistance meter connected to a circuit?
Circuit must be dead.
Connected parallel with the load.
If the circuit is live, damage to the meter or possible explosion of meter due to shorting out the conductors.
Also a possible electric shock from internal voltage.
How is a Volt meter connected to a circuit?
The circuit should be live.
Connected parallel with the conductors.
How is a Ammeter/multimeter connected to a circuit?
The circuit needs to be live.
The meter needs to be connected in series with the load.
If wired in parallel it will short circuit through the meter causing severe damage to the meter.
How is a non-contact voltage tester (hot stick) connected to the circuit?
Circuit needs to be live.
Hold the voltage tester in proximity to the circuit to be tested.
This is not a reliable test to check isolation due to high likelihood of false readings.
How is a wattmeter connected to a circuit?
The circuit needs to be live.
The meter needs to be connected both in series AND in parallel.
The meter needs to be connected while the circuit is isolated, ensure correct wiring to prevent damage to the meter.
Name three safety precautions when using multi-meters.
- Be aware of the circuit, can be working on live conductors.
- Ensure you have the meter set to the correct settings for what you are testing for.
- Know what you are testing for, test the multimeter on a known source first and last to ensure functionality.
- Keep your fingers back behind the guards on the probes.
A 12V circuit has a single 6ohm resistor. How much current would flow in the circuit if the resistor was open circuited?
0 amps.
A 12V circuit has a single 2ohm resistor. How much current would flow in the circuit if the resistor was short circuited?
High current.
It would overload the conductors to the point of failure or tripping a safety device.
