Q: The resistivity of a metal at temperature $$T is $$given by $$\rho(T) = \$$rho_0$$ [1 + \alpha (T - T_0$)]. If$$ $$\$$rho_0$$ = 1.7 \times 10$$^{-8}$$\ \Omega\cdot\text{m}$$, $$\alpha = 0.0039\ \text{K}^{-1}$$, and $$T - T_0$ = 20\ \text{K}$$, what is $$\rho(T)$$?

$$1.83 \times 10$$^{-8}$$\ \Omega\cdot\text{m}$$

Question 1

A flashlight uses a battery to power its bulb. If the battery has an emf of 1.5 V and the bulb draws a current of 0.5 A, how much energy does the battery deliver to the bulb in 10 seconds?

Accepted Answer

$$7.5\ 	ext{J}$$

Question 2

Which statement best describes the direction of conventional current in a metallic conductor?

Accepted Answer

It is opposite to the direction of electron flow.

Question 3

A copper wire has a length $$L$$ and cross-sectional area $$A. $$Its resistance $$R is $$given by:

Accepted Answer

$$R = \frac{\rho L}{A}$$

Question 4

In an ionic solution, such as sodium chloride dissolved in water, the total current is:

Accepted Answer

The sum of the currents due to all types of charged particles.

Question 5

The resistivity of a metal at temperature $$T is $$given by $$ho(T) = \$$rho_0$$ [1 + \alpha (T - T_0$)]. If$$ $$\$$rho_0$$ = 1.7 	imes 10$$^{-8}$$\ \Omega\cdot	ext{m}$$, $$\alpha = 0.0039\ 	ext{K}^{-1}$$, and $$T - T_0$ = 20\ 	ext{K}$$, what is $$ho(T)$$?

Accepted Answer

$$1.83 	imes 10$$^{-8}$$\ \Omega\cdot	ext{m}$$

Question 6

Which material would you expect to have the lowest resistivity at room temperature?

Accepted Answer

Copper

Question 7

A circuit board uses copper traces for conducting paths. Why does current not flow between adjacent traces?

Accepted Answer

The board material is an insulator with very high resistivity.

Question 8

Which graph best represents the temperature dependence of resistivity for a semiconductor?

Accepted Answer

A curve where resistivity decreases as temperature increases.

Question 9

What happens to the resistivity of a superconductor when the temperature drops below its critical temperature $$T_c$$?

Accepted Answer

Resistivity drops abruptly to zero.

Question 10

A resistor obeys Ohm’s law. Which of the following statements is true?

Accepted Answer

The current through the resistor is directly proportional to the voltage across it.

Question 11

A battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to a load. The terminal voltage $$V_{ab} is $$given by:

Accepted Answer

$$V_{ab} = \mathcal{E} - Ir$$

Question 12

A light bulb is connected to a 12 V battery and draws 2 A of current. What is the power consumed by the bulb?

Accepted Answer

$$24\ 	ext{W}$$

Question 13

Which circuit element symbol represents a source of emf with internal resistance?

Accepted Answer

A battery symbol with a resistor in series.

Question 14

A semiconductor diode is a nonohmic resistor. Which of the following best describes its current-voltage relationship?

Accepted Answer

Current increases nonlinearly with voltage in one direction, and little current flows in the opposite direction.

Question 15

If a circuit element has a potential difference $$V_{ab}$$ and a current $$I$$ flowing through it, the power delivered to the element is:

Accepted Answer

$$P = V_{ab} I$$

Question 16

A metallic conductor is heated from $$20^{\circ}$$	ext{C}$$ to 40$$^{\circ}$$	ext{C}. $$What happens to its resistivity?

Accepted Answer

Resistivity increases.

Question 17

Which of the following best explains why a current continues indefinitely in a superconducting ring once established?

Accepted Answer

The resistivity is zero, so there is no energy loss.

Question 18

A resistor has color bands: green, violet, orange, and silver. What is its resistance and tolerance?

Accepted Answer

$$57\ 	ext{k}\Omega$$ with $$\pm 10\%$$ tolerance

Question 19

In a circuit, the potential rises when the current passes through which component?

Accepted Answer

A battery (source of emf)

Question 20

Which equation correctly relates current density $$\vec{J}$$, electric field $$\vec{E}$$, and resistivity $$\rho$$?

Accepted Answer

$$\vec{J} = \frac{\vec{E}}{\rho}$$

Current, Resistance, and Electromotive Force: Study Notes

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