Ohm's Law & Short Circuits

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Questions and Answers

What does Ohm's Law state about the relationship between current and voltage?

  • Current is directly proportional to voltage. (correct)
  • Current is inversely proportional to voltage.
  • Current is independent of voltage.
  • Current is equal to voltage.

A short circuit occurs when a circuit has high resistance.

False (B)

What is the formula used to calculate current in an electric circuit?

I = V/R

As temperature increases, the ______ of a conductor generally increases.

<p>resistance</p> Signup and view all the answers

Match the following components with their purpose:

<p>Resistor = Slows down current Fuse = Prevents excess current Circuit Breaker = Cuts off current in a fault Short Circuit = Allows excess current flow</p> Signup and view all the answers

If the voltage across a toaster is 120 V and the resistance is 14 Ω, what is the current?

<p>8.57 A (C)</p> Signup and view all the answers

Resistance of a conductor remains constant regardless of temperature.

<p>False (B)</p> Signup and view all the answers

What safety devices are commonly used to prevent short circuits?

<p>Fuses and circuit breakers</p> Signup and view all the answers

Ohm's Law can be expressed in the equation V = I x ______.

<p>R</p> Signup and view all the answers

Which of the following represents the correct unit of current?

<p>Amperes (C)</p> Signup and view all the answers

What is the relationship between voltage, current, and resistance as described by Ohm's Law?

<p>Ohm's Law states that the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance.</p> Signup and view all the answers

What is the formula that describes Ohm's Law, and what does each variable stand for?

<p>The formula for Ohm's Law is V = I x R. V represents voltage, I represents current, and R represents resistance.</p> Signup and view all the answers

How does temperature affect the resistance of a conductor?

<p>As temperature increases, the resistance of a conductor generally increases.</p> Signup and view all the answers

What is a short circuit, and what are the potential dangers?

<p>A short circuit is a low-resistance connection between two points in a circuit, often caused by a faulty wire or a loose connection.</p> Signup and view all the answers

What are two safety devices commonly used to prevent short circuits?

<p>Fuses and circuit breakers are two safety devices that can prevent short circuits.</p> Signup and view all the answers

Why is it important to use resistors in electrical circuits?

<p>Resistors are used to slow down the flow of current in a circuit and prevent damage to electrical components.</p> Signup and view all the answers

Explain the concept of direct proportionality in relation to Ohm's Law.

<p>Direct proportionality in Ohm's Law means that voltage and current are directly related. Increasing voltage increases current, conversely, decreasing voltage decreases current.</p> Signup and view all the answers

If a light bulb has a resistance of 100 ohms and is connected to a 120-volt outlet, what is the current flowing through the bulb?

<p>The current flowing through the bulb is 1.2 amps.</p> Signup and view all the answers

What are the units of measurement for voltage, current, and resistance?

<p>The unit of measurement for voltage is the volt (V), for current is the ampere (A), and for resistance is the ohm (Ω).</p> Signup and view all the answers

Why is a short circuit considered dangerous?

<p>Short circuits are dangerous because they allow a large amount of current to flow through a low-resistance connection, potentially causing overheating, fires, or electrocution.</p> Signup and view all the answers

Flashcards

What is Ohm's Law?

Ohm's Law describes the relationship between voltage (V), current (I), and resistance (R) in electrical circuits. It can be represented mathematically as V = I x R.

Resistance and Temperature

The resistance of a conductor stays the same as long as the temperature remains constant.

Current and Voltage Relationship

The current is directly proportional to the voltage. This means that if one increases, the other must also increase.

What is a resistor?

A resistor slows down the flow of electrons in a circuit. It is a device designed to provide resistance and prevent fires by controlling the current.

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What is a short circuit?

An accidental low-resistance connection between two points in a circuit, often causing excessive current to flow.

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How does a short circuit work?

Current flows more easily through the wire path than through the light bulbs, bypassing the intended path. It can be dangerous due to the excessive current flow.

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What are fuses and circuit breakers?

Fuses and circuit breakers are safety devices that prevent short circuits by interrupting the flow of current when it exceeds a safe limit.

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How does temperature affect resistance?

Temperature affects resistance. As temperature increases, resistance increases and conductivity decreases. Conversely, as temperature decreases, resistance decreases, and conductivity increases.

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Rearranging Ohm's Law

The formula V = I x R can be rearranged to solve for current (I) or resistance (R) if two of the variables are known.

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Constant Resistance

As long as temperature stays the same, the resistance of a conductor stays constant.

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Study Notes

Ohm's Law & Short Circuits

  • Ohm's Law describes the relationship between voltage (V), current (I), and resistance (R) in electrical circuits.
  • The formula is represented mathematically as V = I × R
  • If two of the variables are known, the third can be calculated.
  • Alternative formulas: I = V/R and R = V/I
  • Ohm's Law states that the resistance of a conductor remains constant, as long as the temperature stays the same.
  • The current is directly proportional to the voltage; as one increases, so does the other.
  • Temperature affects resistance. As temperature increases, resistance increases and conductivity decreases. Conversely, as temperature decreases, resistance decreases and conductivity increases.
  • A short circuit is an accidental low-resistance connection between two points in a circuit, often causing excess current flow. This is dangerous.
  • Fuses and circuit breakers are safety devices used in electrical circuits to prevent short circuits; they melt or open the circuit when the current is too high.
  • Circuit breakers are reusable, and can be reset when a "fuse is blown". Breakers are commonly found in houses and buildings.
  • A three-pronged plug has a grounding pin that sends extra current to the ground.
  • Ground Fault Circuit Interrupters (GFCIs) are used near water sources. They open the circuit when water gets in the outlet to prevent dangerous electrical shocks.
  • Online resources and textbook pages for further practice are available: sciencesource.ca (login: jcr, pw: jcraccess), and pages 460-461.
  • Practice problems and additional review can be found within the textbook: page 467 #1-12
  • An example of a problem involving Ohm's Law is calculating the current flowing through an electric toaster with a given voltage and resistance: (e.g., V=120 V, R= 14Ω). The result is 8.57A.

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