9.2 - Ohm My Gawd

Properties of a Series Circuit

- I(current) = constant; It = I1 = I2 = I3 - Vt (voltage) = V1 + V2 + V3 - Rt (resistance) = R1 + R2 + R3

Properties of a Parallel Circuit

- It (current)= I1 + I2 + I3 - Vt (voltage) = constant; Vt = V1 = V2 = V3 - 1/Rt (resistance) = 1/R1 + 1/R2 = 1/R3

If you double the diameter of a cylindrical wire, you double its conductivity but reduce its resistivity by one half. True or False?

False

When a potential difference of 10 V is placed across a certain solid cylindrical resistor, the current through it is 2.0 A. If the diameter of this resistor is now tripled, the current will be 18 A. True or False?

False

When a light bulb is connected to a 4.5 V battery, a current of 0.12 A passes through the bulb filament. What is the resistance of the filament? A) 38 ohm B) 28 ohm C) 1.4 ohm D) 9.3 ohm E) 440 ohm

A) 38 ohm

In an electrically neutral atom the number of protons in the nucleus is equal to the number of A) electrons that surround the nucleus. B) neutrons in the nucleus. C) the sum of electrons and neutrons.

A) electrons that surround the nucleus.

Two charged particles held a certain distance apart are released. As they move, the force on each particle increases. Therefore, their charges have A) opposite signs. B) the same size. C) the same mass. D) the same sign.

A) opposite signs.

Each of the resistors in the circuit shown have a resistance of 160.0 Ω. What is the equivalent resistance of the circuit? A)400 ohm B) 160 ohm C) 480 ohm D) 640 ohm

A)400 ohm

What is the SI unit for Current?

Ampere (A)

A 9 V battery is hooked up to two resistors in series. One has a resistance of 5 Ω, and the other has a resistance of 10 Ω. Several locations along the circuit are marked with letters, as shown in the figure. Which statement is true? A) The current at A is greater than the current at B, which is greater than the current at C, which is greater than the current at D. B) The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D. C) The current at A is greater than the current at B, which is equal to the current at C, which is greater than the current at D.

B) The current at A is equal to the current at B, which is equal to the current at C, which is equal to the current at D.

The electric field at point P due to a point charge Q a distance R away has magnitude E. In order to double the magnitude of the field at P, you could A) double the distance to 2R. B) double the charge to 2Q C) reduce the distance to R/4. D) reduce the distance to R/2.

B) double the charge to 2Q

If the length and diameter of a wire of circular cross section are both doubled, the resistance is A) doubled. B) unchanged. C) halved. D) increased fourfold.

C) halved.

A positive ion has more A) protons than neutrons. B) neutrons than protons. C) protons than electrons. D) electrons than protons. E) electrons than neutrons.

C) protons than electrons.

Two charged particles held a certain distance apart are released. As they move, the acceleration of each decreases. Therefore, their charges have A) opposite signs. B) need more information C) the same sign.

C) the same sign.

The resistors in the circuit shown each have a resistance of 600 Ω. What is the equivalent resistance of the circuit? A) 150 ohm B) 2400 ohm C) 1200 ohm D) 600 ohm

D) 600 ohm

Two charged particles repel each other with a force F. If the charge of one of the particles is doubled and the distance between them is also doubled, then the force will be A) F/4. B) F. C) 2 F. D) F/2.

D) F/2.

Two charged particles attract each other with a force F. If the charges of both particles are doubled, and the distance between them also doubled, then the force of attraction will be A) none of them B) F/4. C) 2 F. D) F/2 E) F.

E) F.

Coulomb's Law

F=K |q₁*q₂|/r², magnitude of force between two charges; where K is a constant (9 x 10^9).

Electric field lines begin on negative charges and end on positive charges. True or False?

False

If a 75 W bulb and a 100 W bulb are connected in series across a 120 V outlet, the 75 W bulb will dissipate 75 W of power and the 100 W bulb will dissipate 100 W of power. True or False?

False

Current Density

J = I/A I = Current A = Cross-sectional Area

What is the SI unit for Resistance?

Ohms (Ω)

Equation for charge

Q = ne where N is a +/- integer, and e is the electron charge (coulomb's = 1.6 x 10^-19)

If two point charges exert a force of 1 N on each other when they are 3 cm apart, they will exert a force of 1/25 N when they are 15 cm apart. True or False?

True

In the metal wires of a circuit, the electron current i flows from the negative to the positive end of a battery, but the current I flows from the positive to the negative end of the battery. True or False?

True

The more closely electric field lines are packed together, the stronger the field. True or False?

True

Equation for electrical potential

V (voltage) = E(electric field) x D (distance)

Ohm's Law equation

V (voltage) = I(current)R(resistance)

Potential difference (voltage) between two points

V = Electric field x Length

Drift Velocity equation

Vd = J/q J = current density Q = charge, where n is the value given and e is the electron charge (coulombs = 1/6 x 10^-19).

What is the SI unit for Voltage?

Volts (V) or joules per coulomb

What is the SI unit for Power?

Watt (W)

To become a negative ion, an atom must A) gain a proton. B) lose a proton. C) gain an electron. D) lose an electron.

gain an electron

Equation for resistivity

ρ (resistivity of material) x *L*ength/*A*rea