Ch. 25 - Electric Current and Resistance

Giancoli Douglas - Physics for Scientists and Engineers 5th edition

Giancoli Douglas5th editionPhysics for Scientists and EngineersISBN: 9780137488179당신이 사용하는 게 아니라요?교과서 변경

Giancoli Douglas 5th edition

Ch. 25 - Electric Current and Resistance

문제 86a

24장, 문제 86a

Lightbulb A is rated at 120 V and 40 W for household applications. Lightbulb B is rated at 12 V and 40 W for automotive applications. What is the current through each bulb?

검증된 단계별 안내

Step 1: Recall the formula for power in an electrical circuit:

P = V I

, where

P

is power,

V

is voltage, and

I

is current. Rearrange this formula to solve for current:

I = P / V

Step 2: For Lightbulb A, substitute the given values into the formula. The power

P

is 40 W, and the voltage

V

is 120 V. The current

I

can be calculated as

I = 40/120

(in amperes).

Step 3: For Lightbulb B, substitute the given values into the same formula. The power

P

is 40 W, and the voltage

V

is 12 V. The current

I

can be calculated as

I = 40/12

(in amperes).

Step 4: Ensure that the units are consistent throughout the calculation. Power is in watts (W), voltage is in volts (V), and current will be in amperes (A).

Step 5: After substituting the values and performing the division, you will have the current for each bulb. Remember to double-check your calculations for accuracy.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Ohm's Law

Ohm's Law states that the current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. It is mathematically expressed as I = V/R. This principle is fundamental for calculating current in electrical circuits, especially when voltage and resistance are known.

Power in Electrical Circuits

The power (P) consumed by an electrical device is defined as the product of the voltage (V) across it and the current (I) flowing through it, expressed as P = V × I. This relationship allows us to determine the current if the power rating and voltage are known, which is essential for solving the problem regarding the lightbulbs.

Series and Parallel Circuits

Understanding whether components are connected in series or parallel is crucial for analyzing electrical circuits. In a series circuit, the same current flows through all components, while in a parallel circuit, the voltage across each component is the same. This distinction affects how we calculate current and power for devices like lightbulbs, which can be connected in different configurations.

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