Chapter 23 part 2 Flashcards
Is produced when voltage is applied to a load and current flows through the load.
Power
The ____ the load’s resistance or higher the applied voltage, the ___ power produced.
lower, more
The ____ the load’s resistance or lower the applied voltage, the ___ power produced.
higher, less
The amount of power produced is measured in ___.
Watts(W)
The amount of power produced by a load is equal to the voltage drop across the load times the ___________.
current through the load
What equation is used to calculate total power in a series circuit?
PT = P1 + P2 + P3
What is the total power in a series circuit if three loads are connected in series and each load produces 2W?
PT = P1 + P2 + P3 PT = 2 + 2+ 2 PT = 6W
What is the current in the circuit of a coffee maker during brewing when the applied voltage is 120V and the brew heating element resistance is 16Q?
I = E / R I = 120 / 16 I = 7.5 A
What is the power in a coffee maker’s circuit during brewing when the applied voltage is 120 V and the circuit current is 7.5 A?
P = E x I P = 120 x 7.5 P = 900 W
A coffee pot is warming and we need to find the total resistance. The resistances are 224 Q and 16 Q?
RT = R1 + R2 RT = 224 + 16 RT = 240 Q
What is the current in the circuit during warming when the applied voltage is 120 V and the total circuit resistance is 240 Q ?
I = E / R I = 120 / 240 I = 0.5
What is the power in the circuit during warming when the applied voltage is 120V and the circuit current is 0.5A?
P = E x I P = 120 x 0.5 P = 60 W
Has two or more components connected so that there is more than on path for current to flow.
Parallel connection
Why must care be take when working on parallel circuits?
Care must be taken when working with parallel circuits because current can be flowing in one part of the circuit even though another part of the circuit is turned off.
At least how many switches must be closed to start current flow in a parallel circuit?
One or more switches must be closed
In a parallel circuit how many switches must be opened to stop current flow?
All switches must be opened
Why are switches normally connected in parallel?
to provide additional turn-on points
What is an example of a turn-on switch?
A doorbell. There are switches at the back, front, and side door.
Manually operated switches are often connected in parallel with mechanical and automatic switches. What is an example of this?
The dome light in a car is automatically turned on when the door is opened and automatically turned off when the door is closed. A manual switch (usually built into the headlight switch) is connected in parallel with the door limit switch so that the dome light can be manually turned on.
What is the opposition to current flow?
resistance
The total resistance in a circuit containing parallel-connected loads is _____ than the smallest _________.
less
smallest resistance value
The total resistance _____ if loads are added in parallel and _____ if load are removed.
decreases
increases
What equation is used to calculate total resistance in a parallel circuit containing two resistors?
RT = R1 x R2 / R1 + R2
What is the total resistance in a circuit containing resistors of 300 Q and 600 Q connected in parallel?
RT = R1 x R2 / R1 + R2 RT = 300 x 600 / 300 + 600 RT = 180,000 / 900 RT = 200 Q
What equation is used to calculate total resistance in a parallel circuit with three or more resistors?
RT = 1 / 1/R1 + 1/R2 + 1/R3
What is the total resistance in a circuit containing three resistors of 5000 Q, 2000 Q and 10,000 Q connected in parallel?
RT = 1 / 1/R1 + 1/R2 + 1/R3 RT = 1 / 1/5,000 + 1/2,000 + 1/10,000 RT = 1/.0002 + .0005 + .0001 RT = 1250 Q
The voltage across each load is the same when loads are connected in parallel. The voltage across each load _________ if parallel loads are added or removed.
remains the same
What is the most common method used to connect loads?
Connecting them in parallel
What formula is used to calculate total voltage in a parallel circuit?
ET = E1 = E2 = E3 …….
What is the total voltage if the voltage across each load is measured at 112 VAC with a voltmeter?
ET = E1 =E2 ET = 112 =112 ET = 112 VAC
Total current in a circuit containing parallel connected loads equals the _______.
sum of the current through all the loads
What happens to total current in parallel circuits if loads are added and what happens if loads are taken away?
Total current increases if loads are added and decreases if loads are taken away.
What equation should be used to calculate total current in parallel circuits?
IT = I1 + I2 + I3 + …….
What is the total current in a circuit containing four loads connected in parallel if the current through the four loads is 0.833A, 6.25 A, 8.33 A, and 1.2 A.
IT = I1 + I2 + I3 + I4 IT = 0.833 + 6.25 + 8.33 + 1.2 IT = 16.613 A
What does a loose connection do to circuit resistance and circuit current?
A loose connection increases the circuit resistance and decreases circuit current.
The greater the current flow the ___ the required wire size.
larger
The lesser the current flow, the ___ the required wire size.
smaller
When troubleshooting a circuit, an overloaded circuit has a ___ than normal current reading.
higher
A circuit with a lower-than-expected current reading may have_______.
a loose connection
What does a loose connection do to circuit resistance and circuit current?
A loose connection increases the circuit resistance and decreases the circuit current.
How is power produced in parallel circuits?
Voltage is applied to a load and current flows through the load.
The lower the load’s resistance or higher the applied voltage, ________.
the more power produced
The higher the load’s resistance or the lower the applied voltage______.
the less power produced
Power produced by a load is equal to the voltage drop across the load times _________.
the current through the load
What is total power equal to?
Total power is equal to the sum of the power produced by each load.
What equation is used to calculate total power in a parallel circuit?
PT = P1 + P2 + P3 + P4
What is the total circuit power if four loads are connected in parallel and the loads produce 100 W, 750 W, 1000 W, and 150W?
PT = P1 + P2 + P3 + P4 PT = 100 + 750 + 1000 + 150 PT = 2000 W
Explain how a waffle iron heating using a parallel circuit.
The waffle iron includes a heating element that heats the upper section and a heating element that heats the lower section The two heating elements are connected in parallel. An ON/OFF temperature control switch is used to turn ON the heating elements and control the temperature. A temperature switch is wired in series with the ON/OFF temperature control switch to turn power OFF if over-heating occurs in the circuit.
What is the total power in the waffle iron circuit containing two heating elements with power ratings of 750 W?
PT = P1 + P2 PT = 750 + 750 PT = 1500W
What is the total current in the waffle iron if the total power is 1500 W and the total voltage is 120 V?
IT = P/E IT = 1500/120 IT = 12.5 A
What is the total resistance of the waffle iron if the total voltage is 120 V and the total current I 12.5 A?
RT = E/T RT = 120/12.5 RT = 9.6 Q
