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Slide 1 - Ohm’s Law
- Voltage, Current & Resistance
Slide 2 - Current
- An electrical current is the flow of electrons through a complete circuit.
- The brightness of a light bulb is an indicator of the amount of current (or flow) through the bulb.
- The unit of current is the Ampere (A) or “amp” for short.
Slide 3 - The amount of current that flows in a circuit depends on the resistance of the circuit and the voltage of the source.
- * In other words, a battery does not supply a constant amount of current.
- Current is Variable
Slide 4 - Voltage
- Voltage is the push that drives flow of electrons.
- Voltage in a circuit is determines by the source
- * Batteries will also supply a set amount of voltage (ex. 1.5V, 9V, 12V)
- The unit of voltage is the Volt (V).
Slide 5 - Electrical Potential Energy
- Voltage is the result of a difference in electrical potential energy.
- This is similar to gravitational potential energy, which makes balls roll down hills.
- In this case charges flow from areas of high potential to low potential.
Slide 7 - Resistance
- Resistance is an obstacle to the flow of electrons.
- The total resistance of the circuit impacts the amount of current in the circuit.
- The unit of resistance is the Ohm (Ω).
Slide 8 - Insulators & Conductors
- Different materials and objects have different resistances
- Some objects have a set resistance – like nichrome wire
- Some objects have a variable resistance – like a lightbulb, which has a different resistance when cold v. hot.
- The resistance of an object depends on how tightly the atoms hang on to their electrons.
Slide 10 - Ohm’s Law
- “The current flow through a conductor is directly proportional to the potential difference and inversely proportional to the resistance.”
- In other words: V = IR any of these three values can be found as long as the other two are known.
Slide 11 - Resistance in a Circuit
- When elements are added in series, their total resistance is equal to the sum of their individual resistances:
- Each bulb has a resistance of 0.2 Ω.
- The wire and switch have insignificant resistance.
- What is the total resistance of the circuit?
Slide 12 - 0.5 Ω
- 0.3 Ω