09:59Ohm's law - derivation (using drift velocity)| Electricity | Physics | Khan AcademyKhan Academy India - English577views
Multiple ChoiceA resistor has a current through it of 5 A. If the EMF across the resistor is 10 V, what is the resistance of this resistor?806views16rank
Multiple ChoiceTwo resistors are made of the same material, one twice as long as the other. If the current through the shorter resistor is 5 A, what is the current through the longer resistor if they both have the same potential difference and cross-sectional area?903views13rank
Multiple ChoiceA wire runs from the positive plate of a capacitor, into lightbulb 1, then out from lightbulb 1 directly into lightbulb 2. When lightbulb 2 is connected to the negative plate of the capacitor, what is true about the charge moving through the two lightbulbs?239views
Multiple ChoiceA copper wire with a radius of 2.0 mm and a length of 0.80 m is connected across the terminals of a 9.0 V battery. How much current flows in the wire?288views
Multiple ChoiceA certain wire has length L and radius r, and a resistance of R. That wire is melted down and the same volume of the same metal is used to produce a wire with length 2L. What is the resistance of the resulting wire?409views
Multiple ChoiceA copper wire and an aluminum wire have the same diameter. If the copper wire is 10 m long, how long is the aluminum wire if they have the same resistance?293views1rank
Multiple ChoiceWhich of the following is true about the change in potential across a resistor in a circuit?233views1rank
Textbook QuestionA copper transmission cable 100 km long and 10.0 cm in diameter carries a current of 125 A. (b) How much electrical energy is dissipated as thermal energy every hour?587views
Textbook Question(b) What is the resistance of a carbon rod at 25.8°C if its resistance is 0.0160 Ω at 0.0°C?343views
Textbook QuestionA hollow aluminum cylinder is 2.50 m long and has an inner radius of 2.75 cm and an outer radius of 4.60 cm. Treat each surface (inner, outer, and the two end faces) as an equipotential surface. At room temperature, what will an ohmmeter read if it is connected between (a) the opposite faces and (b) the inner and outer surfaces?301views
Textbook QuestionIn household wiring, copper wire 2.05 mm in diameter is often used. Find the resistance of a 24.0-m length of this wire.349views
Textbook QuestionA ductile metal wire has resistance R. What will be the resistance of this wire in terms of R if it is stretched to three times its original length, assuming that the density and resistivity of the material do not change when the wire is stretched? (Hint: The amount of metal does not change, so stretching out the wire will affect its cross-sectional area.)755views
Textbook QuestionA cylindrical tungsten filament 15.0 cm long with a diameter of 1.00 mm is to be used in a machine for which the temperature will range from room temperature (20°C) up to 120°C. It will carry a current of 12.5 A at all temperatures. (c) What will be the maximum potential drop over the full length of the filament?476views
Textbook QuestionA 2.0-mm-diameter wire formed from a composite material has a resistivity that decreases with distance along the wire as ρ=ρ₀e^−αˣ, where ρ₀=4.0×10^−5 Ω m , x (in m) is measured from one end of the wire, and the constant α=4.0 m^−1. What is the resistance of a 50-cm-long length of this wire?392views
Textbook QuestionA 12 V car battery dies not so much because its voltage drops but because chemical reactions increase its internal resistance. A good battery connected with jumper cables can both start the engine and recharge the dead battery. Consider the automotive circuit of FIGURE P28.64. b. How much current is the dead battery alone able to drive through the starter motor?302views
Textbook QuestionAn idealized ammeter is connected to a battery as shown in Fig. E25.28. Find (c) the terminal voltage of the battery.387views
Textbook QuestionAn idealized ammeter is connected to a battery as shown in Fig. E25.28. Find (b) the current through the 4.00-Ω resistor.575views
Textbook QuestionAn idealized ammeter is connected to a battery as shown in Fig. E25.28. Find (a) the reading of the ammeter.905views
Textbook QuestionThe conductance G of an object is defined as the reciprocal of the resistance R; that is, G = 1/R . The unit of conductance is a mho ( = ohm⁻¹) , which is also called the siemens (S). What is the conductance (in siemens) of an object that draws 380 mA of current at 3.0 V?19views
Textbook Question(III) For some applications, it is important that the value of a resistance not change with temperature. For example, suppose you made a 3.60-k Ω resistor from a carbon resistor and a Nichrome wire-wound resistor connected together so the total resistance is the sum of their separate resistances. What value should each of these resistors have (at 0°C) so that the combination is temperature independent?20views
Textbook Question(II) Compute the voltage drop along an 18-m length of household no. 14 copper wire (used in 15-A circuits). The wire has diameter 1.628 mm and carries a 12-A current.25views
Textbook Question(II) Two aluminum wires have the same resistance. If one has twice the length of the other, what is the ratio of the diameter of the longer wire to the diameter of the shorter wire?27views
Textbook Question(I) What is the resistance of a 5.1-m length of copper wire 1.5 mm in diameter?20views
Textbook Question(II) A bird stands on a dc electric transmission line carrying 3800 A (Fig. 25–35). The line has 2.5 x 10⁻⁵Ω resistance per meter, and the bird’s feet are 4.0 cm apart. What is the potential difference between the bird’s feet?<IMAGE>27views
Textbook Question(II) A rectangular solid made of carbon has sides of lengths 1.0 cm, 2.0 cm, and 4.0 cm, lying along the x, y, and z axes, respectively (Fig. 25–36). Determine the resistance for current that passes through the solid in(a) the x direction (Assume the resistivity is ρ = 3.0 x 10⁻⁵ Ω•m) ,<IMAGE>30views
Textbook Question(II) A rectangular solid made of carbon has sides of lengths 1.0 cm, 2.0 cm, and 4.0 cm, lying along the x, y, and z axes, respectively (Fig. 25–36). Determine the resistance for current that passes through the solid in(b) the y direction, (Assume the resistivity is ρ = 3.0 x 10⁻⁵ Ω•m) and<IMAGE>20views
Textbook Question(II) A rectangular solid made of carbon has sides of lengths 1.0 cm, 2.0 cm, and 4.0 cm, lying along the x, y, and z axes, respectively (Fig. 25–36). Determine the resistance for current that passes through the solid in(c) the z direction. (Assume the resistivity is ρ = 3.0 x 10⁻⁵ Ω•m) .<IMAGE>30views
Textbook Question[In these Problems neglect the internal resistance of a battery unless the Problem refers to it.](II) Eight identical bulbs are connected in series across a 120-V line.(a) What is the voltage across each bulb?41views
Textbook Question(II) A galvanometer has an internal resistance of 32 Ω and deflects full scale for a 48-μA current. Describe how to use this galvanometer to make(a) an ammeter to read currents up to 25 A, and32views
Textbook Question[In these Problems neglect the internal resistance of a battery unless the Problem refers to it.](II) Ten 7.0-W Christmas tree lights are connected in series to each other and to a 120-V source. What is the resistance of each bulb?35views
Textbook Question[In these Problems neglect the internal resistance of a battery unless the Problem refers to it.](II) Eight bulbs are connected in parallel to a 120-V source by two long leads of total resistance 1.4 Ω. If 210 mA flows through each bulb, what is the resistance of each, and what fraction of the total power is wasted in the leads?31views
Textbook Question(II) (a) What is the current in the 13-Ω heating element of a 240-V clothes dryer?(b) How much charge passes through the element in 15 min? (Assume direct current.)31views
Textbook Question(II) A 4.5-V battery is connected to a bulb whose resistance is 2.3 Ω. How many electrons leave the battery per minute?27views
Textbook Question(II) An electric device draws 5.25 A at 240 V.(b) If the resistance of the device were reduced by 7.5%, what current would be drawn at the lower voltage?28views
Textbook Question(II) A silicon diode, whose current–voltage characteristics are given in Fig. 40–38, is connected in series with a battery and an 860-Ω resistor. What battery voltage is needed to produce a 16-mA current?18views