12 Questions
What is the direction of electron flow in a circuit?
from the negative terminal to the positive terminal
What is the unit of electric charge, and what is the charge of an electron?
coulombs, 1.6 × 10^(-19) coulombs
What is the relationship between voltage, current, and resistance according to Ohm's Law?
V = I × R
What is the effect of increasing voltage on current, assuming constant resistance?
increases the current
What is the formula for electric power in terms of voltage and current?
P = V × I
What is the power dissipated by a 250-ohm resistor connected to a 9-volt battery?
0.324 watts, or 324 milliwatts
What is the formula to calculate the power consumed by a circuit, given the voltage and current?
P = VI
If a motor is using 50 watts of power and draws a current of 0.4 amps, what is the voltage across it?
125 volts
What is the formula to calculate the voltage across a circuit, given the current and resistance?
V = IR
If a light bulb consumes 1.8 watts of power, and the cost of electricity is 11 cents per kilowatt-hour, what is the approximate cost of operating the light bulb for a month?
14 cents
What is the current flowing through a 5 kilo-ohm resistor, given that 12.5 coulombs of electric charge flow through it in 8 minutes?
0.026 amps or 26 milliamps
What is the power consumed by a 5 kilo-ohm resistor, given that 12.5 coulombs of electric charge flow through it in 8 minutes?
3.38 watts
Study Notes
- Conventional current is the flow of positive charge from the positive terminal to the negative terminal, whereas electron flow is from the negative terminal to the positive terminal.
- Current is defined as the rate of charge flow, or charge divided by time (Δq / Δt), and its unit is the amp (1 amp = 1 coulomb per second).
- Electric charge is associated with the quantity of charged particles, and an electron has a charge of 1.6 × 10^(-19) coulombs, which is negative.
- Ohm's Law describes the relationship between voltage, current, and resistance, where voltage is the product of current and resistance (V = I × R).
- If the resistance is kept constant, increasing the voltage will increase the current, and increasing the resistance will decrease the current.
- The voltage and current are directly related, while the resistance and current are inversely related.
- Electric power is the product of voltage and current, and it can be expressed in three forms: P = V × I, P = I^2 × R, and P = V^2 / R.
- Power is measured in watts, and 1 watt is equal to 1 joule per second.
- A current of 3.8 amps flowing for 12 minutes results in a charge of 2736 coulombs passing through any point in the circuit.
- The number of electrons represented by this charge is approximately 1.71 × 10^22 electrons.
- A 9-volt battery connected to a 250-ohm resistor results in a current of 0.036 amps, or 36 milliamps.
- The power dissipated by the resistor is 0.324 watts, or 324 milliwatts.
- The power delivered by the battery is equal to the power dissipated by the resistor, which is 0.324 watts.
- A 12-volt battery connected to a light bulb drawing 150 milliamps of current results in an electrical resistance of the light bulb of 80 ohms.
- The power consumed by the light bulb is 1.8 watts.
- The cost of operating the light bulb for a month, given a cost of electricity of 11 cents per kilowatt-hour, is approximately 14 cents.
- A motor using 50 watts of power and drawing a current of 400 milliamps has a voltage across it of 125 volts.- Voltage of the motor is 125 volts.
- Internal resistance of the motor is 312.5 ohms, calculated using Ohm's Law (v = iR) with voltage 125 volts and current 0.4 amps.
- Two important equations in solving common problems are P = VI and V = IR.
- Electric charge flowing through a 5 kilo-ohm resistor is 12.5 coulombs in 8 minutes.
- Electric current is the rate of charge flow, calculated by dividing the change in electric charge by the change in time.
- 8 minutes converted to seconds is 480 seconds.
- Electric current flowing through the resistor is 0.026 amps or 26 milliamps, calculated by dividing the charge (12.5 coulombs) by the time (480 seconds).
- Power consumed by the resistor is 3.38 watts, calculated using the equation P = I^2R with current 0.026 amps and resistance 5 kilo-ohms.
- Voltage across the resistor is approximately 130 volts, calculated using the equation V = IR with current 0.026 amps and resistance 5 kilo-ohms.
Test your understanding of electric circuits, including electric current, voltage, resistance, power, and Ohm's Law. Practice problems and calculations to help you master the basics of electricity.
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