27. Resistors & DC Circuits

You've decided to protect your house by placing a 5.0-m-tall iron lightning rod next to the house. The top is sharpened to a point and the bottom is in good contact with the ground. From your research, you've learned that lightning bolts can carry up to 50 kA of current and last up to 50 μs. You don't want the potential difference between the top and bottom of the lightning rod to exceed 100 V. What minimum diameter must the rod have?

According to Ohm's Law, how many ohms of resistance will allow a current of $1A$ to flow when a voltage of $1V$ is applied across a resistor?

Which of the following is one function of a resistor in a circuit?

According to Ohm's Law, what is the relationship between the current and the voltage across a resistor in a circuit?

In a cylindrical resistor, what is the effect on the resistance if the radius of the vessel is halved, assuming the length and material remain constant? (The resistance $R$ of a cylinder is given by $R=\rho \frac{l}{\pi r^2}$, where $\rho$ is resistivity, $l$ is length, and $r$ is radius.)

Which of the following best describes Ohm's Law?

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

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

A 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?

Two 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?