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What physical quantity changes when a charge moves across a potential difference?

A has four times the power rating of light \(B\) when operating at the same voltage. Is the resistance of light A greater than, less than, or equal to the resistance of light B? Explain.

Find the power dissipated in a \(25-\Omega\) electric heater connected to a \(120-\mathrm{V}\) outlet.

A current of \(2.1\) A flows through an 85- \(\Omega\) resistor. How much power is dissipated?

A circuit contains only a \(12-\mathrm{V}\) battery and a resistor. If a 1.4-A current flows through the resistor, how much power does the resistor dissipate?

A 75-W lightbulb operates at a potential difference of \(95 \mathrm{~V}\). Find (a) the current in the bulb and (b) the resistance of the bulb.

Suppose you charge a comb by rubbing it through your hair. Do you produce a current when you walk across the room carrying the charged comb?

Suppose you charge a comb by rubbing it through the fur on your dog's back. Do you produce a current when you walk across the room carrying the charged comb?

When a battery with a voltage \(V_{0}\) is attached to a resistor with a resistance \(R_{0}\), the resulting current is \(1 \mathrm{~A}\). What is the current in each of the following systems? $$ \begin{array}{|c|c|c|} \hline \text { System } & \text { Voltage } & \text { Resistance } \\ \hline \mathrm{A} & 2 V_{0} & 4 R_{0} \\ \hline \mathrm{B} & 4 V_{0} & 4 R_{0} \\ \hline C & 4 V_{0} & 2 R_{0} \\ \hline \end{array} $$

Explain how electrical devices can begin operating almost immediately after you flip a switch, even though individual electrons in the wire may take hours to reach the device.