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Resistance is a measure of how much a resistor opposes the flow of electric current. To calculate resistance, we utilize Ohm's Law, which states that the voltage across a resistor, denoted as \( V \), is equal to the product of the current through it, \( I \), and its resistance, \( R \): \[ V = IR \]To isolate the resistance, the equation can be rearranged as:\[ R = \frac{V}{I} \]Let's break this down with an example from our exercise. Given a potential difference of 1.50 V and a current of 18.0 mA (or 0.018 A), the resistance can be calculated by plugging these values into the formula:\[ R = \frac{1.50}{0.018} \approx 83.3 \Omega \]This calculated resistance tells us how well the resistor can hinder the flow of the electric current at the specified voltage.Key takeaways:

• Resistance is denoted in ohms (\( \Omega \)).
• To find resistance, divide the voltage by the current.
• Ohm's Law ties voltage, current, and resistance together.

Measuring the current involves understanding how much charge is flowing through a circuit per unit time, typically expressed in amperes (\( A \)). Once the resistance is determined, Ohm's Law can be employed to calculate the current for any given voltage. In our exercise, the resistor initially had a known resistance of \( 83.3 \Omega \). When connected to a 12.6 V car battery, the current can be computed using:\[ I = \frac{V}{R} \]Substituting the given values:\[ I = \frac{12.6}{83.3} \approx 0.151 \mathrm{A} \]This indicates the amount of charge (in this case, 0.151 amperes) moving through the resistor when powered by the car battery.Consider the following points:

• Current tells us how fast electrons are moving through a circuit.
• Higher voltage results in a higher current, assuming the resistance stays the same.
• By altering the voltage or resistance, you can control the current in a circuit.

Potential difference, or voltage, refers to the energy difference per charge between two points in a circuit. It drives the current around the circuit and is measured in volts (\( V \)). To find the voltage, one can use Ohm's Law once again if the current and resistance are known.For example, in the problem, when a current of 0.453 A passes through a resistor of 83.3 \( \Omega \), the voltage of an unknown battery can be determined using:\[ V = IR \]Substituting the known values gives:\[ V = 0.453 \times 83.3 = 37.7 \mathrm{V} \]This new voltage reading tells us that the unknown battery creates a potential difference of 37.7 V across the resistor.Essential points to remember:

• Voltage is the motivating force that drives current around a circuit.
• Higher potential difference results in greater energy transferred per charge.
• Voltage calculations often require knowledge of current and resistance.