A balloon is rubbed quickly across a rug. The balloon is then brought to touch a smooth wall. When released it sticks to the wall. Which of the following explains why the balloon sticks to the wall?
The balloon removes protons from the rug and the extra protons are attracted to the electrons in the wall.
The balloon removes electrons from the rug and those extra electrons from the rug are attracted to the protons in the wall.
The balloon removes protons from the rug and the extra protons are attracted to the protons in the wall.
The balloon removes electrons from the rug and the extra electrons are attracted to the electrons in the wall.
A positively charged conducting sphere sits on an insulated stand. A second insulated neutral conducting sphere is brought near the first but does not touch it. Which statement below best describes the resulting charge distribution?
Loosely held electrons on the neutral sphere are attracted toward the positively charged sphere. The left side of the neutral sphere becomes more negative than the right side as the sphere is polarized.
Loosely held protons on the neutral sphere are repelled away from the positively charged sphere. The left side of the neutral sphere becomes more negative than the right side as the sphere is polarized.
Electrons in each atom of the neutral sphere are pulled closer to the positively charged sphere while the positive atomic nuclei are pushed away slightly. This results in polarization of atoms but not the sphere itself.
Protons jump from the positive sphere onto the neutral sphere, giving both spheres an equal positive charge that is about half of the positive charge that was originally on the left-hand sphere.
A scientist has a neutral conducting sphere on a non-conducting stand, a positively charged conducting rod, and a ground wire (which allows the sphere to be grounded to the Earth). How can the scientist use these to place a charge on the sphere? Select two.
Connect the sphere to the ground wire, bring the rod close to the sphere, disconnect the ground wire, and move the rod away from the sphere. The result is a negatively-charged sphere.
Connect the sphere to the ground wire, bring the rod close to the sphere, move the rod away from the sphere, and disconnect the ground wire. The result is a negatively-charged sphere.
Touch the sphere with the rod without using the ground wire and then move the rod away from the sphere. The result is a positively charged sphere.
Connect the sphere to the ground wire, touch the sphere with the rod, disconnect the ground wire, and then move the rod away from the sphere. The result is a positively charged sphere.
The diagram above shows a circuit with an open switch, a 3 V ideal battery, and a light bulb. Which of the following best represents the magnitude of the potential difference across various elements of this circuit when the switch is open?
It is zero across the switch, bulb, and battery.
It is zero across the switch and bulb, and 3 V across the battery.
It is zero across the bulb, and 3 V across the switch and battery.
It is 3V across the switch, bulb, and battery.
The circuit diagram above shows a closed switch, an ideal battery, and two light bulbs in series. Use this diagram to answer the next two questions. Choose the statement below which correctly describes current in the circuit.
The current leaving the battery is the greatest. It decreases after passing through the first bulb and is zero once it has passed the second bulb.
The current is used up in each light bulb as the charges make the bulbs glow.
The current is the same through all elements of the circuit.
The current through each light bulb is half of that which flows through the battery.
One of the bulbs in the circuit is considerably brighter than the other. Choose the TWO statements below which explain this observation.
The current through both bulbs is the same, so the bulb with the greater resistance will have the greatest potential difference across it and be the brightest.
The potential difference across the two bulbs is the same, so the bulb with the least resistance will have the greatest current through it and be the brightest.
The bulb closest to the positive side of the battery will receive the most current and be the brightest.
The brightest bulb uses the most power as that is a measure of energy output per unit time.
The four cylindrical resistors shown above are made from an alloy of nichrome and have uniform resistivity ρ. If A is the cross-sectional area and L is the length of Resistor A, choose which of the four resistors will have the greatest resistance to electrical current.
Resistor A
Resistor B
Resistor C
Resistor D
A circuit is constructed with two resistors, R1 and R2, in parallel with each other as shown above. The resistance of R2 is greater than the resistance R1. Choose the correct statements from the choices below. There are TWO correct statements.
The potential difference across R2 is the same as the potential difference across R1.
Each electron passing through R2 results in a greater dissipation of energy than each electron passing through R1.
The current is less through R2 than it is through R1.
The power dissipated through R2 is greater than the power dissipated through R1.
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