Physics 2nd term | final exam

Which expression correctly defines electric current?

electric current = ΔQ / Δt

What is the SI unit for current?

Ampere (A)

A light bulb draws a current of 0.835 A. How long does it take for 1.67 C of charge to pass through the filament?

2.00 s

Conventional current is defined as the direction of:

positive charge motion only

Which scientist discovered the connection between physics and biology through "animal electricity"?

Luigi Galvani

Which statement about drift velocity is correct?

Drift velocity is the net velocity of charge carriers in an electric field.

In a copper wire carrying 10.0 A, the drift speed of electrons is about 2.46 × 10-4 m/s. Which conclusion follows?

The electric field change propagates quickly while charges drift slowly.

When an electric field is applied to a conductor, electrons:

undergo repeated collisions with vibrating atoms

Ohm's law in its common form is:

All of the above (each is equivalent)

A device whose current–potential difference graph is nonlinear is called:

non-ohmic

Resistance is defined as the ratio of:

Potential difference to current.

Which component is an example of a non-ohmic device that allows current easily in one direction but not the reverse?

diode

Resistance of a wire increases when:

the temperature of the wire increases

Two wires have identical material and length. Wire A has twice the cross-sectional area of Wire B. Compared to Wire B, the resistance of Wire A is:

half as large

A 1.5 V battery is connected to a bulb with resistance 3.5 Ω. The current through the bulb is:

0.429 A

A circuit has I = 2.5 A and R = 0.6 Ω. The potential difference across the circuit is:

1.5 V

A stereo with R = 65 Ω is plugged into 120 V. Its current is closest to:

1.85 A

Which factor most directly explains why power lines use very high voltages to transmit energy?

High voltage decreases current for a given power, reducing I²R losses.

Electric power P delivered to a resistor can be written as:

All of the above (each is valid)

Which schematic symbol represents a wire or conductor in the diagrams?

Straight line (right-angle corner symbol)

Currents in the human body above disrupt the electrical activity of the heart and can be fatal.

0.15 A

What does a galvanic skin response (GSR) test measure to determine stress?

Decreased resistance due to perspiration

The slope of a Current (I) vs. Potential Difference (∆V) graph for an ohmic material is equal to:

1/R

In a schematic diagram, which symbol best represents a battery's positive terminal?

Longer line of a pair of parallel lines

If you double the potential difference across an ohmic resistor, the current will:

Double.

an electric circuit is defined as:

A path through which charges can flow

Generators differ from batteries because they convert:

Mechanical energy to electrical energy.

In direct current (dc), charges move:

In only one direction.

In the United States, alternating current (ac) oscillates at a frequency of:

60 Hz

Electric power is defined as the rate at which:

Charge carriers do work/convert energy.

The SI unit of power is the:

Watt

1. Which formula represents electric power?

P = I∆V

Which statement is true for resistors connected in series?

The current through each resistor is the same.

Alternative forms for calculating power in ohmic resistors include:

Both a and b

The equivalent resistance for resistors in series is:

The sum of the individual resistances

The unit of energy used by electric companies is the:

Kilowatt-hour (kWh)

One kilowatt-hour (1 kWh) is equivalent to how many Joules?

3.6 x 10⁶ J

Why do household appliances like hair dryers use a lot of energy?

They require a large amount of current to heat the coils.

To minimize energy loss (I2R loss) during transmission, power companies:

Transport energy at high potential differences and low currents.

Power plants may transport electricity at potential differences as high as:

765,000 V

A 9.0 V battery is connected to four resistors in series: 2.0 Ω, 3.0 Ω, 5.0 Ω, and 8.0 Ω. The current in the circuit is:

0.50 A

If a 1050W toaster operates at 120 V, its resistance is approximately:

13.7 ohm

In a series circuit, what happens to the entire circuit if one bulb burns out (open filament)?

The circuit opens and all bulbs go dark.

For resistors connected in parallel across the same voltage source, which is always true?

The potential difference across each resistor equals the source voltage.

As a charge moves through the filament of a light bulb, it:

Loses potential energy due to collisions.

The formula for equivalent resistance of two or more resistors in parallel is:

1 / R_eq = 1 / R₁ + 1 / R₂ + 1 / R₃ + ...

What is the power of a neuron with 70 mV potential difference and 200 mA current?

1.4 10^-2 W

If resistance in a circuit is doubled while voltage remains constant, the power dissipated:

Is halved.

When resistors are placed in parallel, the equivalent resistance must be:

Less than the smallest individual resistance

The typical potential difference provided by a standard wall outlet in a home is:

120 V

What is the primary purpose of a schematic diagram?

To represent the construction of an electrical apparatus using standard symbols

In a schematic diagram, what do straight lines typically represent?

Wires or conductors

Why is a light bulb represented by a symbol with multiple bends?

Because the filament acts as a resistor

According to Figure 1.2, how is the positive terminal of a battery identified in a symbol?

By the longer line

What does a capacitor symbol consisting of two parallel lines of equal length represent?

The physical plates of a capacitor

If a capacitor symbol includes one curved line, what does it indicate?

It can only be used with direct current (DC) sources

How many small circles are used in a switch symbol to indicate contact points?

Two

Which of the following defines an "electric circuit"?

A set of components that provides a complete path for movement of charges

What is a "load" in an electric circuit?

Any element that dissipates energy (e.g., a bulb)

Why are wires and switches usually not considered part of the "load"?

They have negligible resistance

What condition is necessary for a steady current to exist in a circuit?

The circuit must be closed

What happens in an "open circuit"?

There is no charge flow and the current is zero

What defines a "short circuit"?

A circuit with little to no resistance to the movement of charges

Why are short circuits hazardous in a home?

They can cause wires to overheat and start a fire

What percentage of energy in an incandescent bulb is converted to light?

10%

Which practical reason is given in the text for wiring devices (like household appliances) in parallel?

So each device receives the same potential difference and operates independently

Why are LEDs more efficient than incandescent bulbs?

They release almost no energy as heat

What does "emf" stand for in the context of circuits?

Electromotive force

Which device is an example of an emf source?

A battery

What is "internal resistance" in a battery?

Collisions of moving charges with atoms inside the battery

Because of internal resistance, the terminal voltage of a battery is usually:

Slightly less than the emf

According to the law of conservation of energy, the energy gained in the battery must equal:

The energy dissipated by the load

If a flashlight bulb has a potential difference of 3.0 V, what is the potential difference across the batteries powering it?

3.0 V

Why is a bird not electrocuted when perched on a single high-voltage wire?

There is no potential difference between its two feet

The terminal voltage of a battery is:

The potential difference measured across the battery's terminals

What defines a "series" connection in an electric circuit?

Components provide a single path for the current.

In a series circuit, what is true about the current in each resistor?

It is the same for each resistor.

Why must the current be the same for all resistors in a series circuit?

Because charge is conserved and there is only one path.

How is the equivalent resistance (R_eq) calculated for resistors in series?

By adding the individual resistances together (R₁ + R₂ + R₃...).

The equivalent resistance of a series circuit is always:

Greater than any individual resistance.

If a 12.0 V battery is connected to three resistors (6.0 ohm, 15.0 ohm, and 21.0 ohm) in series, what is the equivalent resistance?

42.0 ohm

What happens to a series circuit if one bulb burns out?

There is no current, and all bulbs go dark.

What is one advantage of arranging resistors in series?

It allows several lesser resistances to add up to a greater unavailable resistance.

What defines a "parallel" connection in a circuit?

Components are connected across common points or junctions.

What is true about the potential difference (∆V) across resistors in parallel?

It is the same for each resistor.

In a parallel circuit, if one bulb has less resistance than the others:

More charge moves through it.

The sum of the currents in each branch of a parallel circuit equals:

The total current (I) delivered by the battery.

What formula is used to find the equivalent resistance (R_eq) in parallel?

1/R_eq = 1/R₁ + 1/R₂ + 1/R₃

The equivalent resistance of a parallel circuit is always:

Less than the smallest resistance in the group.

What happens if a bulb burns out in a parallel circuit?

The bulbs in the other branches remain lit.

Why are household circuits arranged in parallel?

To ensure that turning off one appliance doesn't turn off all others.

If the potential difference across a bulb in a flashlight is measured to be 3.0 V, the potential difference across the combination of batteries powering it (neglecting internal resistance per the book's convention) is:

Equal to 3.0 V

The text models a real battery as:

An emf source in series with an internal resistance

How do you find the current in a series circuit?

I = ∆V / R_eq

If four light bulbs with resistances of 2.0 ohm, 4.0 ohm, 5.0 ohm, and 7.0 ohm are connected in parallel to a 9.0 V battery, the equivalent resistance is approximately:

0.917 ohm

A short circuit is hazardous because:

It provides little resistance so current increases and wiring can overheat

How can you tell that car headlights are wired in parallel?

If one headlight burns out, the other stays lit.

What is the equivalent resistance of 57 airplane corridor lights wired in series, if each has a resistance of 2.0 ohm?

114 ohm

In the “Bird on a Wire” conceptual challenge, why is a bird perched on a high-voltage wire usually not electrocuted?

Because there is negligible potential difference between the bird’s two feet

If two resistors (7.25 ohm and 4.03 ohm) are connected in series to a 9.00 V battery, what is the potential difference across the 7.25 ohm resistor?

5.78 V