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Bellringer

Learn about Ohm's Law and the mathematical equations to calculate resistance, voltage, and current. Explore the characteristics of series and parallel circuits, and understand how adding components affects the circuit's resistance and current.

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Bellringer

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  1. Bellringer • Restate Ohm’s Law as 3 different mathematical equations. Resistance = Voltage/Current Voltage = Current X Resistance Current = Voltage/Resistance OR Ohms = Volts/Amps OR Volts = Amps X Ohms OR Amps = Volts/Ohms

  2. Electric Circuits • part II

  3. Series Circuits • A series circuit has all the parts of the circuit connected on one path. • An example of a series circuit is a circuit with a battery and two light bulbs connected by a single wire.

  4. Series Circuits • Suppose a series circuit has two light bulbs. If one burns out, the second bulb goes out because the circuit is broken when the first bulb burns out.

  5. Series Circuits • If you add resistors to a series circuit, the resistance of the circuit increases. • This can be shown as: • RTotal=R1+R2+R3... • Remember, Resistance is measured in Ohms and uses the symbol Ω.

  6. Series Circuits • In a series circuit, the current throughout the circuit is constant. • This can be shown as: • ITotal= I1 = I2 = I3... • Where current is represented by the letter I in the equation, but is measured using the units amperes or amps, and uses the units A.

  7. Series Circuits • Also, in a series circuit, as bulbs are added in line, all of the bulbs become dimmer. • Each bulb adds more resistance to the circuit, therefore, for a constant voltage, when resistance increases, current decreases.

  8. Series Circuits • An ammeter is an instrument used to measure current.

  9. Parallel Circuits • A parallel circuit has more than one path for current to take. There are separate branches in a parallel circuit. Each resistor may be on its own branch.

  10. Parallel Circuits • Suppose a parallel circuit has two light bulbs, each on its own branch. If one light bulb burns out, the other light bulb will stay lit. The second bulb stays lit because it is on its own branch.

  11. Parallel Circuits • Because the voltage source (battery) provides constant voltage, the only factors that can change in a circuit are resistance and current.

  12. Parallel Circuits • In a parallel circuit, when more branches are added, the overall resistance decreases, meaning that the current will increase. • Think blowing through one straw versus blowing through 2 straws. Two straws allow twice as much air through, but your lungs are only capable of blowing so much at a time.

  13. Parallel Circuits • The major disadvantage of a parallel circuit is that as you add more things in parallel, the current draw on the source goes up with each new branch. If the source cannot supply the current that is demanded by the multiple resistors of the circuit, the voltage will (must!) decrease. This could be bad, as some devices, notably motors, do not like to run at low voltage and can actually be damaged if voltage decreases too much.

  14. Parallel Circuits • A voltmeter is a device used to measure voltage, or electrical potential energy difference.

  15. Parallel Circuits • The circuits in your home are parallel. • Electrical energy enters your home through heavy-duty, low resistance wires, and then branch out in parallel to your wall sockets, then to appliances and lights in each room. • The voltage in most household circuits is 120 V.

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