Chapter 17

A heater draws \(8.70 \mathrm{~A}\) on a \(11 \overline{0}-\mathrm{V}\) line. What is its wattage rating?

A cell has an emf of \(1.50 \mathrm{~V}\) and an internal resistance of \(0.0450 \Omega\). If there is \(0.250 \mathrm{~A}\) in the cell, what voltage is applied to the external circuit?

Three resistors of \(2.00 \Omega, 5.00 \Omega\), and \(6.50 \Omega\) are connected in series with a \(24.0-\mathrm{V}\) battery. Find the total resistance of the circuit.

A heating element operates on \(115 \mathrm{~V}\). If it has a resistance of \(24.0 \Omega\), what current does it draw?

Find the resistance of \(78.0 \mathrm{~m}\) of No. 20 aluminum wire at \(20^{\circ} \mathrm{C}\). \((\rho=2.83 \times\) \(\left.10^{-6} \Omega \mathrm{cm}, A=2.07 \times 10^{-2} \mathrm{~cm}^{2} .\right)\)

An electric field has a positive test charge of \(4.00 \times 10^{-5} \mathrm{C}\) placed on it. The force on it is \(0.600 \mathrm{~N}\). What is the magnitude of the electric field at the test charge location?

Two identical charges, each \(-8.00 \times 10^{-5} \mathrm{C}\), are separated by a distance of \(25.0 \mathrm{~cm} .\) What is the force of repulsion?

What power is needed for a sander that draws \(3.50 \mathrm{~A}\) and has a resistance of \(6.70 \Omega ?\)

The voltage applied to a circuit is \(11.8 \mathrm{~V}\) when the current through the battery is \(0.500 \mathrm{~A}\). If the internal resistance of the battery is \(0.150 \Omega\), what is the emf of the battery?

A coffeepot operates on \(12.0 \mathrm{~V}\). If it draws \(2.50 \mathrm{~A}\), find its resistance.

Find the resistance of \(315 \mathrm{ft}\) of No. 24 copper wire with resistance \(0.0262 \Omega / \mathrm{ft}\).

What is the field magnitude of an electric field in which a negative charge of \(2.00 \times 10^{-8} \mathrm{C}\) experiences a force of \(0.0600 \mathrm{~N} ?\)

The force of repulsion between two identical positive charges is \(0.800 \mathrm{~N}\) when the charges are \(0.100 \mathrm{~m}\) apart. Find the value of each charge.

How many amperes will a \(75.0\) -W lamp draw on a \(11 \overline{0}-\mathrm{V}\) line?

The emf of a battery is \(12.0 \mathrm{~V}\). If the internal resistance is \(0.300 \Omega\) and the voltage applied to the circuit is \(11.6 \mathrm{~V}\), what is the current through the battery?

An electric heater draws a maximum of \(14.0 \mathrm{~A}\). If its resistance is \(15.7 \Omega\), on what voltage is it operating?

Find the resistance per foot of No. 22 copper wire if \(580 \mathrm{ft}\) has a resistance of \(9.57 \Omega\)

An electric field exerts a force of \(2.50 \times 10^{-4} \mathrm{~N}\) on a positive test charge of \(5.00 \times 10^{-4} \mathrm{C}\). Find the magnitude of the field at the charge location.

A charge of \(+3.0 \times 10^{-6} \mathrm{C}\) exerts a force of \(940 \mathrm{~N}\) on a charge of \(+6.0 \times 10^{-6} \mathrm{C}\). How far apart are the charges?

A heating coil operates on \(22 \overline{0} \mathrm{~V}\). If it draws \(15.0 \mathrm{~A}\), find its resistance.

At \(77^{\circ} \mathrm{F}, 10 \overline{0} \mathrm{ft}\) of No. 18 copper wire has a resistance of \(0.651 \Omega\). Find the resistance of \(500 \mathrm{ft}\) of this wire.

An electric field exerts a force of \(3.00 \times 10^{-4} \mathrm{~N}\) on a positive test charge of \(7.50 \times 10^{-4} \mathrm{C}\). Find the magnitude of the field at the charge location.

A charge of \(-3.0 \times 10^{-8} \mathrm{C}\) exerts a force of \(0.045 \mathrm{~N}\) on a charge of \(+5.0 \times 10^{-7} \mathrm{C}\). How far apart are the charges?

How many amperes will a \(75 \overline{0}\) -W lamp draw on a \(11 \overline{0}-\mathrm{V}\) circuit?

Five \(9.00-\mathrm{V}\) cells, each with an internal resistance of \(0.100 \Omega\) and a current output of \(0.750 \mathrm{~A}\), are connected in parallel to form a battery in a certain circuit. (a) Find the current in the external circuit. (b) What is the emf of the battery? (c) Find the internal resistance of the battery.

Find the resistance that draws \(0.750 \mathrm{~A}\) on \(115 \mathrm{~V}\).

Find the resistance of \(475 \mathrm{~m}\) of No. 20 copper wire at \(20^{\circ} \mathrm{C}\). \((\rho=1.72 \times\) \(\left.10^{-6} \Omega \mathrm{cm}, A=2.07 \times 10^{-2} \mathrm{~cm}^{2} .\right)\)

An electric field of magnitude \(0.450 \mathrm{~N} / \mathrm{C}\) exerts a force of \(8.00 \times 10^{-4} \mathrm{~N}\) on a test charge placed in the field. What is the magnitude of the test charge?

When a \(-9.0-\mu \mathrm{C}\) charge is placed \(0.12 \mathrm{~cm}\) from a charge \(q\) in a vacuum, the force between the two charges is \(850 \mathrm{~N}\). What is the value of \(q\) ?

What current does a \(75.0-\Omega\) resistance draw on \(115 \mathrm{~V} ?\)

Find the resistance of \(10 \overline{0} \mathrm{~m}\) of No. 20 copper wire at \(20^{\circ} \mathrm{C} .(\rho=1.72 \times\) \(\left.10^{-6} \Omega \mathrm{cm}, A=2.07 \times 10^{-2} \mathrm{~cm}^{2} .\right)\)

An electric field of magnitude \(0.370 \mathrm{~N} / \mathrm{C}\) exerts a force of \(6.20 \times 10^{-4} \mathrm{~N}\) on a test charge placed in the field. What is the magnitude of the test charge?

How far apart are two identical charges of \(+6.00 \mu \mathrm{C}\) if the force between them is \(25.0 \mathrm{~N} ?\)

Six \(50.0-\mathrm{W}\) bulbs are operated for \(25.0 \mathrm{~h}\) on a \(115-\mathrm{V}\) circuit. If energy costs $$\$ 0.075$$ per $\mathrm{kWh}$$, find the cost of operating them.

Using the formulas for series and parallel circuits, fill in the blanks in the tables shown opposite each circuit. In the blanks across from Battery under \(V\) : Write the emf of the battery. \(I\) : Write the total current in the circuit. \(R\) : Write the equivalent or total resistance of the entire circuit. In the blanks across from \(R_{1}\) under \(V\) : Write the voltage drop across \(R_{1}\). \(I:\) Write the current flowing through \(R_{1}\). \(R\) : Write the resistance of \(R_{1}\). In the blanks across from \(R_{2}, R_{3}, \ldots\), fill in the appropriate numbers under \(V, I\), and R. (Begin by looking for key information given in the table and work from there.)

A heater operates on \(22 \overline{0} \mathrm{~V}\). If it draws \(12.5 \mathrm{~A}\), what is its resistance?

Find the resistance of \(50.0 \mathrm{~m}\) of No. 20 aluminum wire at \(20^{\circ} \mathrm{C}\). \((\rho=2.83 \times\) \(10^{-6} \Omega \mathrm{cm}, A=2.07 \times 10^{-2} \mathrm{~cm}^{2} .\)

What force is exerted on a test charge of \(3.86 \times 10^{-5} \mathrm{C}\) if it is placed in an electric field of magnitude \(1.75 \times 10^{4} \mathrm{~N} / \mathrm{C}\) ?

Three charges are located along the \(x\) -axis. Charge \(A(+3.00 \mu \mathrm{C})\) is located at the origin. Charge \(B(+5.50 \mu \mathrm{C})\) is located at \(x=+0.400 \mathrm{~m}\). Charge \(C(-4.60 \mu \mathrm{C})\) is located at \(x=+0.750 \mathrm{~m} .\) (a) Find the total force (and direction) on charge \(B\). (b) Find the total force (and direction) on charge \(A\). (c) Find the total force (and direction) on charge \(C\).

A small furnace uses \(3.00 \mathrm{~kW}\) of power. If the cost of operation of the furnace is $$\$ 3.84$$ for a \(24.0\) -h period, what is the cost of energy per \(\mathrm{kWh}\) ?

What current does a \(50.0-\Omega\) resistance draw on \(115 \mathrm{~V} ?\)

Find the length of copper wire with resistance \(0.0262 \Omega / \mathrm{ft}\) and total resistance \(3.00 \Omega\).

What force is exerted on a test charge of \(4.00 \times 10^{-5} \mathrm{C}\) if it is placed in an electric field of magnitude \(3.00 \times 10^{6} \mathrm{~N} / \mathrm{C} ?\)

Three charges are located along the \(x\) -axis. Charge \(A(+5.00 \mu \mathrm{C})\) is located at the origin. Charge \(B(+4.50 \mu \mathrm{C})\) is located at \(x=+0.650 \mathrm{~m}\). Charge \(C(-4.20 \mu \mathrm{C})\) is located at \(x=+0.650 \mathrm{~m}\). Find the total force (and direction) on charge \(B\).

Will a 20.0-A fuse blow if a \(1000-\mathrm{W}\) hair dryer, a \(1200-\mathrm{W}\) electric skillet, and an \(11 \overline{0} 0-\mathrm{W}\) toaster are all used at once on a \(11 \overline{0}-\mathrm{V}\) line?

What current does a \(175-\Omega\) resistance draw on \(22 \overline{0} \mathrm{~V} ?\)

Find the cross-sectional area of copper wire at \(20^{\circ} \mathrm{C}\) that is \(60.0 \mathrm{~m}\) long and has resistivity \(\rho=1.72 \times 10^{-6} \Omega \mathrm{cm}\) and resistance \(0.788 \Omega\).

How long could you operate a \(1000-\mathrm{W}\) soldering iron for \(\$$ 0.50\) if the cost of energy is $$\$ 0.075 /\( \mathrm{kWh} ?\)

A heater draws \(3.50 \mathrm{~A}\) on \(115 \mathrm{~V}\). What is its resistance?

Find the length of a copper wire with resistance \(0.0262 \Omega / \mathrm{ft}\) and total resistance \(5.62 \Omega\)