Exam 21: Electric Charge and Electric Field

Internal battery resistance: The emf and the internal resistance of a battery are shown in the figure. If a current of 7.8 A is established through the battery from b to a, what is the terminal voltage V_ab of the battery?

Drift velocity: Building codes usually limit the current carried by a 1.6-mm diameter copper wire to 15 A. Many household circuits are wired with this size wire. What is the drift velocity of the electrons in this case?. Assume one conduction electron per atom in copper. The atomic weight of copper is 63.3 g/mol and its density is 8900 kg/m³. Avogadro's number is 6.022 × 10²³ molecules/mol and e = 1.60 × 10^-19 C.

Drift velocity: When electric current is flowing in a metal, the electrons are moving

Power: A certain electric furnace consumes 24 kW when it is connected to a 240-V line. What is the resistance of the furnace?

Internal battery resistance: The emf and the internal resistance of a battery are as shown in the figure. When the terminal voltage V_ab is equal to 17.4 V, what is the current through the battery, including its direction?

Drift velocity: The figure shows a steady electric current passing through a wire with a narrow region. What happens to the drift velocity of the moving charges as they go from region A to region B and then to region C?

Power: The resistivity of gold is 2.44 × 10^-8 Ω ∙ m at room temperature. A gold wire that is 1.8 mm in diameter and 11 cm long carries a current of 170 mA. How much power is dissipated in the wire?

Resistivity and temperature: A Nichrome wire is used as a heating element in a toaster. From the moment the toaster is first turned on to the moment the wire reaches it maximum temperature, the current in the wire drops by 20.0% from its initial value. What is the temperature change in the wire? The temperature coefficient of resistivity for Nichrome is 0.000400 (°C)^-1.

Current density: A certain fuse "blows" if the current in it exceeds 1.0 A, at which instant the fuse melts with a current density of What is the diameter of the wire in the fuse?

Drift velocity: The figure shows two connected wires that are made of the same material. The current entering the wire on the left is 2.0 A and in that wire the electron drift speed is v_d. What is the electron drift speed in the wire on the right side?

Ohm's law: Two cables of the same length are made of the same material, except that one cable has twice the diameter of the other cable. When the same potential difference is maintained across both cables, which of the following statements are true? (There may be more than one correct choice.)

Basics of ac circuits: A 500-W device is connected to a 230-V ac power source. What rms current flows through this device?

Current: In a certain electroplating process gold is deposited by using a current of 14.0 A for 19 minutes. A gold ion, Au⁺, has a mass of approximately 3.3 × 10^-22 g. How many grams of gold are deposited by this process?

Electric field in a wire: A narrow copper wire of length L and radius b is attached to a wide copper wire of length L and radius 2b, forming one long wire of length 2L. This long wire is attached to a battery, and a current is flowing through it. If the electric field in the narrow wire is E, the electric field in the wide wire is

Resistivity and temperature: The temperature coefficient of resistivity for copper is 0.0068 (C°)^-1. If a copper wire has a resistance of 104 Ω at 20°C, what is its resistance 80°C?

Current: The current in a wire varies with time according to the equation I(t) = 6.00 A + ( 4.80 A/s)t, where t is in seconds. How many coulombs of charge pass a cross section of the wire in the time period between t = 0.00 s and

Current density: If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm, what is the average current density in this wire?

Basics of ac circuits: A 500-W device is connected to a 230-V ac power source. What peak current flows through this device?

Internal battery resistance: The emf and the internal resistance of a battery are as shown in the figure. If a current of 8.3 A is drawn from the battery when a resistor R is connected across the terminals ab of the battery, what is the power dissipated by the resistor R?

Power: A light bulb is connected to a 110-V source. What is the resistance of this bulb if it is a 100-W bulb?