Q: A seawater salinity probe passes $$1\,\mu\text{A} of $$current between its electrodes. How many coulombs of charge pass between the electrodes every second?

$$1 \times 10$$^{-6}$$\,\text{C}$$

Q: Which equation represents the conservation of current at a junction?

$$\sum I_{\text{in}} = \sum I_{\text{out}}$$

Q: At a junction, three wires carry currents of $$3\,\text{A}$$, $$2\,\text{A}$$, and $$4\,\text{A}$$ into the junction, and one wire carries $$6\,\text{A}$$ out. What is the current in the remaining wire, and in which direction does it flow?

$$3\,\text{A}$$ into the junction

Question 1

Which of the following best describes the physical meaning of electric current in a conductor?

Accepted Answer

The rate at which charge passes through a cross-sectional area of the conductor.

Question 2

A lightbulb in a string of holiday lights glows because:

Accepted Answer

Current flows through the filament, transferring energy and causing it to emit light.

Question 3

If a charged parallel-plate capacitor is discharged through a wire, which of the following is NOT observed?

Accepted Answer

The plates gain more charge as the wire discharges.

Question 4

Which equation correctly defines electric current $$I$$?

Accepted Answer

$$I = \frac{\Delta q}{\Delta t}$$

Question 5

A seawater salinity probe passes $$1\,\mu	ext{A} of $$current between its electrodes. How many coulombs of charge pass between the electrodes every second?

Accepted Answer

$$1 	imes 10$$^{-6}$$\,	ext{C}$$

Question 6

In a metal, conduction electrons are:

Accepted Answer

Free to move throughout the solid, not bound to any particular atom.

Question 7

What is the net displacement of an electron in a metal under the influence of an electric field?

Accepted Answer

Opposite to the direction of the electric field.

Question 8

A wire is connected between two points of different potential. What causes electrons to move through the wire?

Accepted Answer

An electric field pointing from higher to lower potential.

Question 9

Which equation represents the conservation of current at a junction?

Accepted Answer

$$\sum I_{	ext{in}} = \sum I_{	ext{out}}$$

Question 10

At a junction, three wires carry currents of $$3\,	ext{A}$$, $$2\,	ext{A}$$, and $$4\,	ext{A}$$ into the junction, and one wire carries $$6\,	ext{A}$$ out. What is the current in the remaining wire, and in which direction does it flow?

Accepted Answer

$$3\,	ext{A}$$ into the junction

Question 11

A battery provides an emf $$\mathcal{E} to a $$circuit. Which equation correctly relates the potential difference across the battery to its emf?

Accepted Answer

$$\Delta V_{	ext{bat}} = \mathcal{E}$$

Question 12

If three $$1.5\,	ext{V}$$ batteries are connected in series, what is the total emf supplied to the circuit?

Accepted Answer

$$4.5\,	ext{V}$$

Question 13

A $$50\,	ext{W}$$ light bulb carries a current of $$0.43\,	ext{A}$$ when turned on. How much charge passes through the lightbulb in $$1$$ minute?

Accepted Answer

$$25.8\,	ext{C}$$

Question 14

Which of the following statements about batteries and emf is correct?

Accepted Answer

The battery's emf is the energy supplied per unit charge.

Question 15

In a circuit, what happens to the energy of a charge as it moves from the negative terminal to the positive terminal of a battery?

Accepted Answer

It gains energy equal to $$q \Delta V_{	ext{bat}}.$$

Question 16

Which of the following factors does NOT affect the flow of current in a conductor?

Accepted Answer

The color of the conductor.

Question 17

A PH & Salinity Monitor uses a current to measure ion concentration in water. Which principle is this based on?

Accepted Answer

The relationship between current and the number of charge carriers.

Question 18

In the microscopic model for current, what is the role of collisions between electrons and ions?

Accepted Answer

They reset the motion of electrons, causing a net drift opposite to the electric field.

Question 19

Which of the following best explains why a compass needle is deflected when a wire discharges a capacitor?

Accepted Answer

The flow of current in the wire produces a magnetic field.

Electric Current and Electromotive Force (EMF): Foundations of Electric Circuits

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