Chapter 17: Section 3

Make calculations involving Ohm’s Law

Give examples of how resistors work in common appliances

Explain the relationship between current, voltage, and resistance

The equation below is the most important equation in the study of electric circuits

∆V = I • R

This equation is known as Ohm's law Ohm’s law predicts the relationship

between potential difference, current and resistance.

The Ohm's law equation can be rearranged and expressed as

Resistance (R) is measures in ohms (Ω) The potential difference (∆V) is

measured in volts (V) Current (I) is measured in amps

This Ohm’s law equation relates the two variables that would affect the amount of current in a circuit. The current in a circuit is directly

proportional to the electric potential difference

The greater the battery voltage (i.e., electric potential difference), the greater the current.

On the other hand, current is inversely proportional to the total resistance offered by the external circuit. The greater the resistance, the less the

current. Charge flows at the greatest rates

when the battery voltage is increased and the resistance is decreased.

Because current is affected by resistance, resistors are often used in the circuits of electrical appliances to affect the amount of current present in various components.

By increasing or decreasing the amount of resistance in a particular branch of a circuit, a manufacturer can increase or decrease the amount of current in that branch.

Appliances such as electric mixers and light dimmer switches operate by altering the current This is done by increasing or decreasing

the resistance of the circuit.

Pushing the various buttons on an electric mixer can change the mode from mixing to beating by reducing the resistance and allowing more current to be present in the mixer.

Similarly, turning a dial on a dimmer switch can increase the resistance of its built-in resistor and thus reduce the current.

A walkman uses a standard 1.5 V battery. How much resistance is in the circuit if it uses a current of 0.01 A? 150 ohms