# Electrical Circuits and Ohm's Law

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## 12 Questions

### What is the unit of electric current, and how is it defined?

The unit of electric current is the ampere (A), and it is defined as 1 coulomb per second (1 A = 1 C/s).

### What is the direction of flow of conventional current and electron flow in a circuit?

Conventional current flows from the positive terminal to the negative terminal, whereas electron flow is from the negative terminal to the positive terminal.

### What is the relationship between voltage, current, and resistance according to Ohm's Law?

The voltage (V) is equal to the product of current (I) and resistance (R), i.e., V = I × R.

### How does the voltage and resistance affect the current in a circuit?

If the resistance is kept constant, increasing the voltage will increase the current, and increasing the resistance will decrease the current.

### What is electric power, and how is it related to voltage and current?

Electric power (P) is the product of voltage (V) and current (I), i.e., P = V × I.

### What is the relationship between electric power and resistance?

The electric power (P) can also be expressed as P = I^2 × R or P = V^2 / R, showing the relationship with resistance (R).

### What is the relationship between the power delivered by a battery and the power dissipated by a resistor?

The power delivered by the battery is equal to the power dissipated by the resistor.

125 volts

312.5 ohms

### What is the electric current flowing through a 5 kilo-ohm resistor if 12.5 coulombs of electric charge flow through it in 8 minutes?

26 milliamps or 0.026 amps

3.38 watts

### What is the voltage across the resistor if the electric current flowing through it is 26 milliamps and the resistance is 5 kilo-ohms?

approximately 130 volts

## 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, Ohm's Law, and related concepts such as voltage, current, resistance, and power. Covers calculations of electric charge, current, and power consumption.

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