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Just as water flows from a region of high pressure to a region of low pressure, electric charge flows from a region of |
high electric pressure to a region of low electric pressure. |
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Just as in hydraulic circuits there is water pressure, in electric circuits there is |
voltage |
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An ampere is a unit of electric |
current |
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Electrons flow in a wire when there is |
a potential difference across its ends. |
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A suitable electric pump in an electric circuit is a |
generator & chemical battery |
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It is correct to say that in electric circuits |
*voltage is the ratio of energy per charge. *voltage is applied across a circuit. *flowing charge is current. *charge flows through a circuit. |
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A coulomb of charge flowing in a bulb filament powered by a 6-volt battery is provided with |
6 joules |
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If you stretch a copper wire so that it is thinner, the resistance between its ends |
increases |
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Two light bulbs are connected to a battery, one at a time. The bulb that draws more current has the |
lower resistance, and is brightest. |
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When you turn on a lamp, the initial current in its filament is greater at first, rather than a moment later, which indicates |
increased temperature means increased resistance. |
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Electric resistance in our skin is lowered when our skin is |
moist |
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Current in a conductor can be increased by |
*reducing its resistance. *increasing the voltage across it. |
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The resistance of a filament that carries 2 A when a 10-V potential difference across it is |
5 ohms |
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Two lamps with different filament thicknesses, and therefore different resistances, are connected in series. Greater current is in the lamp with the |
same in each |
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If an electric toaster rated at 110 V is accidently plugged into a 220-V outlet, the current drawn by the toaster will be |
twice its normal value |
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The current in two identical light bulbs connected in series is 0.25 A. The voltage across both bulbs is 110 V. The resistance of a single light bulb is |
220 ohms |
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Direct current is normally produced by a |
battery |
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Alternating current is normally produced by a |
generator |
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Current that is typically 60 hertz is |
alternating current |
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A capacitor is useful in |
smoothing pulsed current |
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An electric diode is useful for |
changing ac to dc |
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For electric current in the home, your power company supplies |
energy |
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The source of electrons in a simple electric circuit is |
the electrical circuit itself |
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Electrons that are energized to glow in the filament of a common ac lamp are |
electrons already in the filament. |
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The number of electrons delivered daily to an average American home by an average power utility in the early 21st century was |
zero |
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When Eddie Electron experiences an electrical shock, the source of electrons composing the shock is |
eddie’s body |
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Electrons flow in an electrical circuit by |
Electrons flow in an electrical circuit by |
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The drift speed of electrons that compose current in a flashlight is about |
less than 1 cm/s. |
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The electric field established by a generator in an ac circuit |
changes magnitude and direction with time. |
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Power is defined as the energy expended per unit of time. When translated to electrical terms, power is equal to |
current multiplied by voltage. |
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In units of measurement, power in watts is equal to |
amperes x volts. |
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One joule per coulomb is a unit of |
voltage. |
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One kilowatt is a unit of |
power |
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One kilowatt-hour is a unit of |
energy. |
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The electric power supplied to a lamp that carries 2 A at 120 V is |
240 watts. |
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A 100-W lamp glows brighter than a 25-W lamp. The electrical resistance of the 100-W lamp is |
less |
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The energy dissipated in a light bulb in a circuit is provided by the |
voltage source. |
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A 60-W light bulb connected to a 120-V source draws a current of |
0.5 A. |
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The power consumed by a device drawing 0.8 A when connected to 120 V is |
96 W. |
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A power line with a resistance of 2 ohms carries a current of 80 A. The power dissipated in the line is |
12,800 W. |
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A 60-W and a 100-W light bulb are rated at 120V. Which bulb has a higher resistance? |
60-W bulb |
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A 60-W and a 100-W light bulb are connected in parallel to a 120-V outlet. Which bulb draws more current? |
100-W bulb |
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The current drawn by a 1200-W toaster connected to 120 V is 10 A. The resistance of the toaster coils is |
12 ohms. |
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A heater draws 20A when connected to a 110-V line. If the electric power costs 20 cents per kilowatt hour, the cost of running the heater for 10 hours is |
$4.40. |
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A lamp rated 23W 120V means that it will deliver 23 W |
when the voltage across it is 120 V. |
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The amount of current in a CFL rated 23W 120V is about |
0.2A. |
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If you wish to keep chicken warm in a shed on a cold night, the best lamp to use is |
an incandescent lamp. |
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By convention, the direction of current in a circuit is |
*the direction in which positive charge flows. *from the positive terminal of a source to the negative terminal. |
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When two lamps are connected in parallel to a battery, the electrical resistance that the battery senses is |
less than the resistance of either lamp. |
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On some early automobiles both headlights failed when one bulb burned out. The headlights were likely connected in |
series. |
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Compared to a single lamp connected to a battery, two identical lamps connected in series to the same battery will carry |
less current. |
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Connect a pair of lamps in series and current is drawn from the battery. Connect the same lamps in parallel and the current drawn is |
more |
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The safety fuse in an electric circuit is connected to the circuit in |
series |
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As more lamps are connected in a series circuit, the overall current in the power source |
decreases |
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To connect a pair of resistors so their equivalent resistance (the single resistor having their combined value) will increase, connect them in |
series |
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The equivalent resistance of any parallel branch in a circuit is |
always less than the resistance of the lowest resistor. |
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A 4-ohm and 6-ohm resistor connected in parallel have an equivalent resistance of |
2.4 ohms. |
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Three resistors take the shape of a triangle, one resistor in each leg. Resistance in one leg is 4 ohms, 6 ohms in a second leg, and a third leg 10 ohms. Connecting an ohm-meter across the 10-ohm resistor will show the equivalent resistance to be |
5 ohms. |
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The equivalent (combined) resistance of 1-ohm, 2-ohm, and 3-ohm in series is about |
6 ohms. |
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