27. Resistors & DC Circuits

Which of the following best describes Ohm's Law?

Which of the following is the SI unit for electrical resistance?

How long must a 0.60-mm-diameter aluminum wire be to have a 0.50 A current when connected to the terminals of a 1.5 V flashlight battery?

FIGURE EX27.35 is a current-versus-potential-difference graph for a material. What is the material's resistance?

Neglect the internal resistance of a battery unless the problem refers to it. 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?

If a resistor has the color bands green, blue, brown, and gold, what is its resistance and tolerance?

A 1.5 V battery provides 0.50 A of current. At what rate (C/s) is charge lifted by the charge escalator?

An idealized ammeter is connected to a battery as shown in Fig. E$25.28$. Find the current through the $4.00$-$\Omega$ resistor.

Electronic devices often use an RC circuit to protect against power outages as shown in Fig. 26–84. (a) If the protector circuit is supposed to keep the supply voltage at least 75% of full voltage for as long as 0.20 s, how big a resistance R is needed? The capacitor is 7.6 μF. Assume the attached “electronics” draws negligible current. (b) Between which two terminals should the device be connected, a and b, b and c, or a and c?

A 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. What will be the maximum potential drop over the full length of the filament?

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?

Neglect the internal resistance of a battery unless the problem refers to it. 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?

An electric device draws 5.25 A at 240 V. If the resistance of the device were reduced by 7.5%, what current would be drawn at the lower voltage?