91Ó°ÊÓ

In a parallel circuit, each device operates independently. This means the current flowing through each device can be calculated separately. Using the formula for electrical power, \( P = IV \), where \( P \) is the power in watts, \( I \) is the current in amperes, and \( V \) is the voltage in volts. You can solve for current with the equation \( I = \frac{P}{V} \). For example, in the given problem:
- The toaster, with a power rating of \( 1650 \text{ W} \), draws a current of \( 13.75 \text{ A} \) using \( I = \frac{1650}{120} \).
- The iron, rated at \( 1090 \text{ W} \), draws about \( 9.08 \text{ A} \).
- The microwave oven, rated at \( 1250 \text{ W} \), draws approximately \( 10.42 \text{ A} \).
Each device in parallel adds its current to the total current drawn from the source. Thus, the total current is simply the sum of all these individual currents.

A circuit breaker is an essential safety device in electrical circuits. It protects an electrical circuit from damage caused by an overload or short circuit. It works by interrupting the flow of electrical current when it exceeds a designated safe level. The breaker "opens" or "trips" to stop the current. This prevents the wiring from overheating and possibly causing fires. In our example, the circuit breaker is rated at \( 20 \text{ A} \). If the total current surpasses this value, the breaker will open.
From our calculations, the total current drawn by the toaster, iron, and microwave is about \( 33.25 \text{ A} \). Since this total is well above the breaker's safe limit, the breaker will indeed "open" to protect the circuit. The circuit breaker effectively safeguards against scenarios where too much power is drawn from the circuit.

In a parallel circuit, determining equivalent resistance is slightly more complex than in series circuits. The total or "equivalent" resistance \( R_{\text{eq}} \) in a parallel configuration is derived from the formula \[\frac{1}{R_{\text{eq}}} = \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \ldots\]Each device’s resistance is found via \( R = \frac{V}{I} \). In the case of the toaster, iron, and microwave:
- Toaster resistance \( R_1 \approx 8.73 \Omega \)
- Iron resistance \( R_2 \approx 13.22 \Omega \)
- Microwave resistance \( R_3 \approx 11.52 \Omega \)
Substitute these resistances into the equation to find \( R_{\text{eq}} \).
When you do the math, you find \( R_{\text{eq}} \approx 5.23 \Omega \). The lower equivalent resistance in parallel circuits means they allow more current to flow than a single device would under the same conditions.