physics chapter 14 test review
Explain Kirchhoff 's current law.
(applies to parallel circuits) the current entering a point in a circuit is equal to the current flowing out of the point
Explain Kirchhoff 's voltage law.
(applies to series circuits) The sum of the voltage drops across the bulbs is the same as the voltage of the battery
How frequently does the alternating current used in the United States reverse direction?
60 times per second
A light bulb has a power of 60 watts. Explain what this means in terms of energy and time.
60J of energy per second
According to _____, if a circuit contains a 3-volt battery, the voltage drops around the complete circuit must add to 3 volts.
Kirchhoff's Voltage Law
_____ states that all the current entering a point in a circuit must also leave that point.
Kirchhoff's current Law
A circuit contains a 12 volt battery and two 3-ohm bulbs in series.find the current in the circuit and the voltage drop across each bulb.
Rt=6ohms It=12V/6ohms It=2A V=IR V=(2A)(3A) V=6V
How do you calculate the total resistance of two parallel resistors?
Rt=R1xR2/R1+R2
parallel circuit contains a 6-volt battery and two 6-ohm bulbs. Use the formula for combining parallel resistors to calculate the total resistance of the circuit.
Rt=R1xR2/R1+R2 Rt=3ohms
What happens to the total resistance of a parallel circuit as more branches are added? Why?
Th total resistance decreases. there are more paths for the current to flow and more current flows for the same voltage drop.
Electrical appliances in your home use _____ current.
alternating
What is the purpose of the AC adapter on the end of the cord used for cell phones?
changes 120V alternating current available at wall receptacles into low voltage direct current
A battery creates _____ current.
direct
The rate of converting electrical energy into another form of energy is called _____.
electrical power
One _____ is equal to 746 watts.
horsepower
One _____ equals 1000 watts.
kilowatt
The _____ is a unit used by electric utility companies to measure the electrical energy your home uses each month.
kilowatt-hour
What is the meaning of the kilowatt-hour?
kilowatts per hour
how to calculate kw-hr
kwxhrs=kw-hrs
Do longer or shorter wires have more resistance?
longer
A _____ contains multiple paths or branches for the current.
parallel circuit
A _____ contains only one path for the current.
series circuit
A _____ is created when a circuit contains one branch with very little or no resistance.
short circuit
Why can short circuits be dangerous?
short circuits allow large currents to flow which can generate enough heat to melt the wire and cause a fire.
Do thinner or thicker wires have more resistance?
thinner
Why is it dangerous to connect several extension cords to make one long cord?
too long wires will cause a voltage drop and appliances may not work properly
A _____ converts high-voltage electricity to lower voltage electricity.
transformer
There is a _____ across each resistor in a circuit when current is flowing.
voltage drop
