# Current Electricity Questions and Answers

Physics

Current ElectricityA home uses 400 kWh of electricity during peak hours and 300 kWh during off-peak hours. The power company charges 15¢/kWh for peak consumption and 10¢/kWh for off-peak use. How much is the homeowner's energy bill? Show all your calculations for full mark.

Physics

Current ElectricityA resistor is measured to have a resistance of 252 Q. What is the potential difference across the resistor when it carries a current of 75.0 mA?
18900 V
16.4 V
3.36 V
18.9 V

Physics

Current ElectricityWhat is the potential difference across the terminals of a battery if 45 kJ of energy
is required to move 500.0 C of charge?
0.090 V
22 500 V
90 V
9.0 V

Physics

Current ElectricityTwo identical batteries each of emf E = 2 volt and internal resistance r = 1 ohm are available to produce heat in an exlernal resistance by passing a current through it. What is the maximum power that can be developed across an external resistance R using these batteries.
A. 4W
B. 8W
C. 6W
D. 2W

Physics

Current ElectricityThe resistivity of gold is 2.44 × 10-8 • m at a temperature of 20°C. A gold wire, 1.8 mm in diameter and 14 cm long, carries a current of 480 mA. The power dissipated in the wire is closest to: B) 0.31 mW C) 0.077 mW D) 0.19 mW A) 0.14 mW

Physics

Current ElectricityA motor is 80% efficient. How much usefull work can the motor do if it is supplied with 200kW.h of energy?

Physics

Current ElectricityShow that the drift speed of free electrons in a wire does not depend on the cross-sectional area of the wire.

Physics

Current ElectricityThe heater element of a particular 120-V
toaster is a 8.9-m length of nichrome wire,
whose diameter is 0.86 mm. The resistivity of
nichrome at the operating temperature of the
toaster is 1.3 × 10-6. m. If the toaster is
operated at a voltage of 120 V, how much
power does it draw?
800 W
750 W
700 W
770 W
720 W

Physics

Current ElectricityWhen you attach a 1.00 m long section of wire to the ends of a 1.50 V battery you measure the current in the wire to be 8.00 A. If the diameter of the wire is 3.33 x 10-4m, what is its
resistivity?

Physics

Current ElectricityIn the circuit below, all four resistors are identical (R₁ = R₂ = R3 = R₁ = R) and the battery has a voltage of 4.82 V.
(a) When the switch is placed in position 1, the measured current in the battery is 1.39 mA. What is the value of each resistor?
(b) When the switch is placed in position 2, what is the current flowing out of the battery?
(c) When the switch is open (neither in position 1 or position 2), what is the current flowing out of the battery?

Physics

Current ElectricityThe length of a certain wire is kept same while its radius is doubled. What is the new
resistivity of this wire?
E) It does not change.
C) It is reduced by a factor of 2.
B) It is increased by a factor of 4.
D) It is reduced by a factor of 4.
A) It is increased by a factor of 2.

Physics

Current ElectricityEqual potentials are applied on an iron and a copper wire of same length. In order to have the same current flow in the two wires, the ratio r (iron) / r (copper) of their radii must be : [Give that : specific resistance of copper = 1.7 x 10-8 ohm - m ]:

Physics

Current ElectricityWhich of these statements is true about resistors connected in series?
Both the current passing through and the potential drop across each resistor are different.
The same amount of current will pass through each resistor.
Both the current passing through and the potential drop across each resistor are the same.
The potential drop across each resistor will be the same.

Physics

Current ElectricityA small insect crawls in the direction of electron drift along copper wire that carries a current of 2.56A. It travels with drift speed of the electron in the wire of uniform cross- section area 1 mm² . Number of free elections for copper = 8 x 1022 /cc and resistivity of copper = 1.6 × 10-Nm . How much time would the insect take to crawl 1.0 cm if it crawls at the drift speed of the electons in the wire?

Physics

Current ElectricityThree charges are arranged in the (x, y) plane as shown. What is the magnitude of the resulting force (in nano-Newtons) on the -9 nC charge at the origin? The Coulomb constant is 8.98755 x 10 N·m²/C² Answer in units of N. part 2 of 2 What angle does the resultant force on the -9 nC charge at the origin make with the positive axis? Quadrant I lies between (f and 90°, quadrant II between between 90° and 180 etc. Answer in units of degs.

Physics

Current ElectricityYou are planning a circuit where you need a resistor with a value of 4.22 Ohms (2). This resistor is made out of gold (see the table in your textbook for information about gold). This resistor will be cylindrical with a radius of 3.19 μm. You can assume that the resistor is being used at the standard 20 degrees Celsius. What length must your resistor be in order to have the needed resistance of 4.22 Ohms? Make sure to put your answer in an appropriate number of significant figures. Put your answer in to the box in units of cm.