Electric Charge, Current and Potential Difference

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Questions and Answers

A series circuit contains a 12V battery and two resistors, 4Ω and 2Ω. What is the current flowing through the 2Ω resistor?

2 Amperes

A heating element in a device has a resistance of 20Ω and draws a current of 5A. Calculate the power consumed by the heating element.

500 Watts

A 10-meter long wire has a resistance of 5Ω. If the wire is cut in half, what is the resistance of each half, assuming uniform resistivity?

2.5 Ohms

A device operates at 120V and consumes 60W of power. What is the current flowing through it?

0.5 Amperes Signup and view all the answers

A copper wire has a length of 2 meters and a cross-sectional area of $1 \times 10^{-6} m^2$. Given that the resistivity of copper is $1.7 \times 10^{-8} Ω⋅m$, what is the resistance of the wire?

0.034 Ohms Signup and view all the answers

A light bulb is rated at 100W and 120V. Calculate the resistance of the bulb's filament when it is operating at its rated power.

144 Ohms Signup and view all the answers

A heating element dissipates 1200 J of heat in 2 minutes when a current of 2A passes through it. What is the resistance of the heating element?

5 Ohms Signup and view all the answers

How does the resistance of a conductor change if its length is doubled and its cross-sectional area is halved?

The resistance quadruples. Signup and view all the answers

Explain how the microscopic movement of electrons results in the macroscopic phenomenon of electric current in a conductor.

The cumulative directed movement of numerous free electrons within the conductor, propelled by an electric field, constitutes the electric current. Although individual electrons move randomly, the overall drift is directional, leading to a net charge flow. Signup and view all the answers

A copper wire and a nichrome wire have the same length and cross-sectional area. If a potential difference is applied across each wire, which wire will have a larger current, and why?

The copper wire will have a larger current when the same potential difference is applied. Copper has a lower resistivity than nichrome, meaning it offers less resistance to the flow of electric charge. Signup and view all the answers

Describe the relationship between potential difference, current, and resistance as expressed by Ohm's Law. Give an example of how you could apply Ohm's Law to calculate an unknown quantity in a circuit.

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, and inversely proportional to the resistance between them ($V = IR$). For instance, if a 12V battery is connected to a resistor with a resistance of 4 ohms, the current flowing through the resistor would be 3 amps ($12V = I * 4\Omega$). Signup and view all the answers

Explain how the length and cross-sectional area of a wire affect its resistance. Use an analogy (e.g., water flowing through a pipe) to illustrate these relationships.

The longer the wire, the greater the resistance because electrons have to travel a greater distance, encountering more obstacles. The wider the wire, the lower the resistance, because there is more space for electrons to flow. Using the water pipe analogy, a longer pipe increases resistance to water flow, while a wider pipe decreases resistance. Signup and view all the answers

Differentiate between conductors, semiconductors, and insulators in terms of their ability to conduct electric current, and provide one common use for each type of material.

Conductors easily allow current flow (e.g., copper wires in circuits). Semiconductors have intermediate conductivity that can be controlled (e.g., silicon in transistors). Insulators strongly resist current flow (e.g., rubber coating on wires). Signup and view all the answers

Describe the difference between a series and a parallel circuit. What happens to the overall resistance and current in each type of circuit when more resistors are added?

In a series circuit, components are connected along a single path, increasing overall resistance and decreasing current as more resistors are added. In a parallel circuit, components are connected in separate branches, decreasing overall resistance and increasing total current as more resistors are added. Signup and view all the answers

Explain the concept of 'quantization of charge'. What is the fundamental unit of charge, and how does it relate to the charge of other particles?

Quantization of charge means that electric charge exists only in integer multiples of a fundamental unit of charge ($e = 1.602 imes 10^{-19}$ Coulombs), which is the magnitude of the charge carried by a single proton or electron. The charge of any object is always an integer multiple of this fundamental charge. Signup and view all the answers

A negatively charged rod is brought near a neutral metallic sphere. Describe the distribution of charge on the sphere and explain why this occurs. What would happen if the rod touched the sphere?

The negative charge of the rod repels electrons in the sphere, causing them to redistribute such that there is an excess of positive charge on the side of the sphere near the rod and an excess of negative charge on the opposite side. If the rod touched the sphere, some electrons would transfer from the rod to the sphere, charging the sphere negatively. Signup and view all the answers

Explain how a household fuse protects electrical appliances during a sudden surge in current. What property of the fuse wire is key to its function?

A fuse protects appliances by melting and breaking the circuit when a sudden surge in current occurs. This prevents damage to other components. The key property is the fuse wire's low melting point. Signup and view all the answers

A lightbulb is rated at 60W and operates at 120V. Calculate the current flowing through the bulb when it is in normal operation.

Using the formula $P = VI$, where P is power, V is voltage, and I is current, we rearrange to solve for I: $I = P/V = 60W/120V = 0.5A$. Therefore, the current flowing through the bulb is 0.5 amps. Signup and view all the answers

A heating element in an electric kettle has a resistance of 20 ohms and draws a current of 10 amps. Calculate the power consumed by the heating element.

Using the formula $P = I^2R$, where P is power, I is current, and R is resistance: $P = (10A)^2 * 20Ω= 2000W$. So, the power consumed by the heating element is 2000 watts. Signup and view all the answers

Define electric power and state its SI unit. How is electric power related to electric energy?

Electric power is the rate at which electrical energy is consumed or transferred in a circuit. Its SI unit is the watt (W), which is equivalent to one joule per second (J/s). Electric energy is the product of electric power and time. Signup and view all the answers

An electric iron consumes 2.1 kWh of energy in 3 hours. Calculate the power rating of the electric iron.

Using the formula $E = P*t$, where E is energy, P is power, and t is time, we rearrange to solve for P: $P = E/t = 2.1 kWh / 3 h = 0.7 kW$. Therefore, the power rating of the electric iron is 0.7 kW or 700 watts. Signup and view all the answers

A resistor has a voltage of 12V across it and a current of 2A flowing through it. Calculate the resistance of the resistor.

Using Ohm's Law, $V = IR$, where V is voltage, I is current, and R is resistance, we can rearrange to solve for R: $R = V/I = 12V / 2A = 6Ω.$ Thus, the resistance of the resistor is 6 ohms. Signup and view all the answers

Explain how the resistivity of a material is affected by its length and cross-sectional area. Provide the formula that relates these quantities.

Resistivity is a material property that is independent of its dimensions. The resistance (R) of a wire is directly proportional to its length (l) and inversely proportional to its cross-sectional area (A), described by the formula: $R = \rho (l/A)$, where $\rho$ is the resistivity. Signup and view all the answers

A 100-watt light bulb is left on for 24 hours. If the cost of electricity is $0.10 per kilowatt-hour, calculate the cost of the energy consumed.

First, convert watts to kilowatts: 100W = 0.1 kW. Calculate the energy consumed: $E = P*t = 0.1 kW * 24 h = 2.4 kWh$. Finally, calculate the cost: Cost = 2.4 kWh * $0.10/kWh = $0.24. Signup and view all the answers

Flashcards

Electric Charge

The physical property causing matter to experience force in an electromagnetic field.

Positive Charge

Loss of electrons results in this type of charge.