### Extended Response

### 19.1 Ohm's law

61.

Describe the relationship between current and charge. Include an explanation of how the direction of the current is defined.

- Electric current is the charge that passes through a conductor per unit time. The direction of the current is defined to be the direction in which positive charge would flow.
- Electric current is the charges that move in a conductor. The direction of the current is defined to be the direction in which positive charge would flow.
- Electric current is the charge that passes through a conductor per unit time. The direction of the current is defined to be the direction in which negative charge would flow.
- Electric current is the charges that move in a conductor. The direction of the current is defined to be the direction in which negative charge would flow.

62.

What could cause Ohmâ€™s law to break down?

- If small amount of current flows through a resistor, the resistor will heat up so much that it will change state, in violation of Ohmâ€™s law.
- If excessive amount of current flows through a resistor, the resistor will heat up so much that it will change state, in violation of Ohmâ€™s law.
- If small amount of current flows through a resistor, the resistor will not heat up so much and it will not change its state, in violation of Ohmâ€™s law.
- If excessive amount of current flows through a resistor, the resistor will heat up so much that it will not change its state, in violation of Ohmâ€™s law.

63.

You connect a single resistor $R$ across a $10\text{-V}$ battery and find that $0.01\phantom{\rule{thinmathspace}{0ex}}\text{A}$ flows through the circuit. You add another resistor $R$ after the first resistor and find that $0.005\phantom{\rule{thinmathspace}{0ex}}\text{A}$ flows through the circuit. If you have $10$ resistors $R$ connected in a line one after the other, what would be their total resistance?

- $\frac{R}{10}$
- $5\phantom{\rule{thinmathspace}{0ex}}\text{R}$
- $\frac{10}{R}$
- $10\phantom{\rule{thinmathspace}{0ex}}\text{R}$

### 19.2 Series Circuits

64.

Explain why the current is the same at all points in the circuit below.

- If the current were not constant, the mobile charges would bunch up in places, which means that the voltage would decrease at that point. A lower voltage at some point would push the current in the direction that further decreases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which means that the voltage would increase at that point. But a higher voltage at some point would push the current in the direction that decreases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which mean that the voltage would increase at that point. A higher voltage at some point would push the current in the direction that further increases the voltage.
- If the current were not constant, the mobile charges would bunch up in places, which mean that the voltage would decrease at that point. But a lower voltage at some point would push the current in the direction that increases the voltage.

65.

What is the current through each resistor in the circuit?

- Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and*R*_{4}is 0.48 A, 0.30 A, 1.2 A, and 0.24 A, respectively. - Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and*R*_{4}is 1200 A, 1920 A, 480 A, and 2400 A, respectively. - Current through resistors
*R*_{1},*R*_{2},*R*_{3}, and is*R*_{4}2.08 A, 3.34 A, 0.833 A, and 4.17 A, respectively. - The same amount of current, 0.096 A, flows through all of the resistors.

### 19.3 Parallel Circuits

66.

In a house, a single incoming wire at a high potential with respect to the ground provides electric power. How are the appliances connected between this wire and the ground, in parallel or in series? Explain.

- The appliances are connected in parallel to provide different voltage differences across each appliance.
- The appliances are connected in parallel to provide the same voltage difference across each appliance.
- The appliances are connected in series to provide the same voltage difference across each appliance.
- The appliances are connected in series to provide different voltage differences across each appliance.

### 19.4 Electric Power

67.

A single resistor is connected across the terminals of a battery When you attach a second resistor in parallel with the first, does the power dissipated by the system change?

- No, the power dissipated remain same.
- Yes, the power dissipated increases.
- Yes, the power dissipated decreases.

68.

In a flashlight, the batteries are normally connected in series. Why are they not connected in parallel?

- Batteries are connected in series for higher voltage and power output.
- Batteries are connected in series for lower voltage and power output.
- Batteries are connected in series so that power output is a much lower for the same amount of voltage.
- Batteries are connected in series to reduce the overall loss of energy from the circuit.