H Physics Current Test (Frew and HW only) [look over notes later]

1 Ampere =

1 coulomb/1 second

T/F:in a parallel circuit, the change in potential accross each element is the same

True

capacitator

a device used to store charge in a circuit

circuit

a system where current can flow through

Resistors in series have the same

current

what does a 1.5V battery store?

energy

the internal resistance of a voltmeter is

infinite ohms

why does playdoh conduct electricity?

it is an ionic conductor due to high salt and water content

switchs should be wired in series with what they control

true

the internal resistance of an ammeter is

zero ohms

The terminals of a battery are connected across two different resistors in parallel. Which of the following statements are correct? (Select all that apply.) The voltage difference is greater across the resistor closer to the battery. The voltage difference across the larger resistor is greater than the voltage difference across the smaller resistor. The larger resistor carries more current than the smaller resistor. The larger resistor carries less current than the smaller resistor. The voltage difference across each resistor is the same.

1. The larger resistor carries less current than the smaller resistor. 2. The voltage difference across each resistor is the same.

When resistors with different resistances are connected in series, which of the following must be the same for each resistor? Choose all correct answers. potential difference current power delivered charge entering each resistor in a given time interval none of those answers

1. current 2. charge entering each resistor in a given time interval

A metal wire of resistance R is cut into four equal pieces that are then placed together side by side to form a new cable with a length equal to one-fourth the original length. What is the resistance of this new cable?

1/16 R

A wire carries a current of 1.6 A. How many electrons per second pass a given point in the wire? Choose the best estimate.

10^19

Two lightbulbs are each connected to a voltage of 120 V. One has a power of 25 W, the other 100 W. Which bulb has the higher resistance? Which bulb carries more current?

25W; 100W

Three resistors, A, B, and C, are connected in parallel and attached to a battery, with the resistance of A being the smallest and the resistance of C the greatest. Which resistor carries the highest current? A B C All wires carry the same current. More information is needed to answer the question.

A

HW66#1: The capacitor in the figure below has a large capacitance and is initially uncharged. After the switch is closed, what happens to the lightbulb?

It glows for a very short time as the capacitor is being charged.

Two sets of Christmas tree lights are available. For set A, when one bulb is removed, the remaining bulbs remain illuminated. For set B, when one bulb is removed, the remaining bulbs do not operate. Explain the difference in wiring for the two sets.

Set A is a parallel system while Set B is a series system. Set A is a parallel system because the elements have their own path to the power source. Set B is a series system because the elements have the same single path to the power source.

we have seen that an electric field must exist inside a conductor that carries a current. How is that possible in view of the fact that in electrostatics we concluded that the electric field must be zero inside a conductor?

Since there isn't supposed to be any charge inside a conductor, and the charge inside is neutral, there can't be an electric field. There has to be a negative or positive charge or charges in order for there to be a field.

If charges flow very slowly through a metal, why does it not require several hours for a light to come on when you throw a switch?

The charges don't flow quickly. However, the force that acts on the charges is strong. The battery creates an electric field that spreads through the electrical wires at the speed of light.

The terminals of a battery are connected across two different resistors in series. Which of the following statements are correct? (Select all that apply.) The current in each resistor is the same. The larger resistor carries less current. The smaller resistor carries more current. The voltage difference is greatest across the resistor closest to the positive terminal. The voltage difference across each resistor is the same.

The current in each resistor is the same.

When the voltage across a certain conductor is doubled, the current is observed to triple. What can you conclude about the conductor?

This conductor doesn't follow Ohm's Law because voltage and current are supposed to be inversely proportional.

An LED light has polarity. waht does this mean for an LED?

This means that an LED has to be orientated in a certain direction in order for current to flow.

what is the pourpose of a wire in a current?

a passage for current to flow through

short circuit

a short circuit is an alternate pathway that accidentally gives more extra energy and bypasses something that was meant to be on.

How is a circuit breaker wired? a. in series with the device it is protecting b. in parallel with the device it is protecting c. neither in series or in parallel d. it is impossible to tell

a. in series with the device it is protecting

Car batteries are often rated in ampere-hours. Does this information designate the amount of current, power, energy, charge or potential that the battery can supply?

charge. Because The rate of charge flow past a given location is coulombs over seconds, which is also what amperes are.

an ammeter measures

current that flows through the machine

T/F: switchs should be wired in parallel with what they control

false

an ammeter is properpy placed in parallel with the element its measuring

false

in a parallel circuit, the current is the same through each element

false

in a series circuit, the changes in potential accross each element is the same

false

the voltmeter is properly placed in series with the element its measuring

false

The rules of series and parallel connections can be used to solve for the total resistance in all circuits.

false (kirkoffs laws, werent in series or parallel)

at night, a person charges their phone, the battery gains electrons

false, it stores energy

in order to function properly, how must a voltmeter be combined with the circuit element to be measured?

parallel

a voltmeter measures

potential difference between volts

resistors in parallel have the same

potential difference.

in order to function properly, how must an ammeter be combined with the circuit element to be measured?

series

should switchs be in series or in parallel with the items they control?

series

T/F: in a DC resistor circuit, a wire is equipotential, or surface of constant voltage

true

a short circuit decreases resistance and thus increases current

true

according to ohms law, current and resistance are inversely proportional

true

in a dc resistor circuit, a wire is equipotential or surface of constant voltage

true

in a parallel circuit, the change in potential across each element is the same

true

the conventional current travels from higher potential to lower potential even tho electrons are really moving in opposite directions in a wire

true

the resistance of a piece of copper depends on its length and cross sectional area

true

what is the voltage drop (∆v) across an ammeter while it measures current?

∆v=ir=infinite(0)=0v