Electrical Energy and Power - Electromotive force

• Definition: The electromotive force (emf) of a device is the work done per unit charge in moving a charge around a complete circuit.
• Symbol: emf (ε)
• Unit: volt (V)

Electrical Energy and Power - Electromotive force (Continued)

• The emf of a cell or a battery is the energy supplied by the cell or battery per unit charge delivered to the external circuit.
• The emf of a device is typically greater than the potential difference across the device when it is connected in a circuit.
• The potential difference across a device in a circuit is equal to the emf minus the potential drop across the internal resistance of the device.

Electrical Energy and Power - Internal resistance

• Definition: The internal resistance of a device is the resistance offered by the components inside the device to the flow of current.
• Symbol: r
• Unit: ohm (Ω)

Electrical Energy and Power - Internal resistance (Continued)

• The internal resistance of a device is responsible for the potential drop across the device when current flows through it.
• The internal resistance of a device is constant for a given device and is determined by the materials and construction of the device.
• When the internal resistance of a device is high, the potential difference across the device decreases, resulting in reduced current flow.

Electrical Energy and Power - Power in circuits

• The power (P) in an electrical circuit is the rate of energy transfer or the rate at which work is done.
• Power is equal to the product of the potential difference (V) across the device and the current (I) flowing through it.
• Formula: P = V * I
• Unit: watt (W)

Electrical Energy and Power - Power in circuits (Continued)

• The power dissipated by a device can be calculated using the formula: P = I^2 * R, where R is the resistance of the device.
• In a series circuit, the total power supplied by the source is equal to the sum of the power dissipated by all the devices in the circuit.
• In a parallel circuit, the total power supplied by the source is equal to the sum of the power supplied to all the devices in the circuit.

Electrical Energy and Power - Energy transfer in circuits

• Electrical energy (E) is the product of power (P) and time (t).
• Formula: E = P * t
• Unit: joule (J)
• The total electrical energy transferred in a circuit is equal to the product of the power and the time for which the device is connected to the circuit.

Electrical Energy and Power - Energy transfer in circuits (Continued)

• The electrical energy transferred to a device can be calculated using the formula: E = V * Q, where Q is the charge that passes through the device.
• The unit of electrical energy, joule (J), is equivalent to one watt-second (W·s).
• One kilowatt-hour (kWh) is equal to 3.6 million joules (3.6 MJ) and is commonly used as a unit of electrical energy.

Electrical Energy and Power - Power loss

• In a circuit, power loss occurs due to resistance in the wires and components.
• The power loss can be calculated using the formula: P_loss = (I^2) * R_loss, where R_loss is the resistance causing the power loss.
• To minimize power loss in a circuit, it is important to use wires and components with low resistance.
• Power loss is dissipated as heat and can cause inefficiency in electrical devices.

Electrical Energy and Power - Electromotive force

• Definition: The electromotive force (emf) of a device is the work done per unit charge in moving a charge around a complete circuit.
• Symbol: emf (ε)
• Unit: volt (V)
• The emf of a cell or a battery is the energy supplied by the cell or battery per unit charge delivered to the external circuit.
• The emf of a device is typically greater than the potential difference across the device when it is connected in a circuit.
• The potential difference across a device in a circuit is equal to the emf minus the potential drop across the internal resistance of the device.

Electrical Energy and Power - Internal resistance

• Definition: The internal resistance of a device is the resistance offered by the components inside the device to the flow of current.
• Symbol: r
• Unit: ohm (Ω)
• The internal resistance of a device is responsible for the potential drop across the device when current flows through it.
• The internal resistance of a device is constant for a given device and is determined by the materials and construction of the device.
• When the internal resistance of a device is high, the potential difference across the device decreases, resulting in reduced current flow.

Electrical Energy and Power - Power in circuits

• The power (P) in an electrical circuit is the rate of energy transfer or the rate at which work is done.
• Power is equal to the product of the potential difference (V) across the device and the current (I) flowing through it.
• Formula: P = V * I
• Unit: watt (W)
• The power dissipated by a device can be calculated using the formula: P = I^2 * R, where R is the resistance of the device.
• In a series circuit, the total power supplied by the source is equal to the sum of the power dissipated by all the devices in the circuit.

Electrical Energy and Power - Power in circuits (Continued)

• In a parallel circuit, the total power supplied by the source is equal to the sum of the power supplied to all the devices in the circuit.
• Power can also be calculated using the formula: P = (I^2) * r, where r is the internal resistance of the device.
• The power delivered to the load is maximum when the internal resistance of the source is equal to the resistance of the load.
• The power delivered to a device can be controlled by either adjusting the potential difference or the resistance in the circuit.
• High power devices such as heaters and motors have low resistance and require higher potential difference to operate.

Electrical Energy and Power - Energy transfer in circuits

• Electrical energy (E) is the product of power (P) and time (t).
• Formula: E = P * t
• Unit: joule (J)
• The total electrical energy transferred in a circuit is equal to the product of the power and the time for which the device is connected to the circuit.
• Energy is not consumed or destroyed in a circuit, but rather is transferred and transformed into other forms such as heat, light, or mechanical work.
• In practical applications, it is important to consider the efficiency of devices, which is the ratio of useful energy output to the total energy input.

Electrical Energy and Power - Energy transfer in circuits (Continued)

• The electrical energy transferred to a device can also be calculated using the formula: E = V * Q, where Q is the charge that passes through the device.
• The unit of electrical energy, joule (J), is equivalent to one watt-second (W·s).
• One kilowatt-hour (kWh) is equal to 3.6 million joules (3.6 MJ) and is commonly used as a unit of electrical energy.
• To calculate the cost of electrical energy consumed, the number of kilowatt-hours used is multiplied by the cost per kilowatt-hour.
• It is important to conserve electrical energy and make efficient use of devices to reduce the consumption and cost of energy.

Electrical Energy and Power - Power loss

• In a circuit, power loss occurs due to resistance in the wires and components.
• The power loss can be calculated using the formula: P_loss = (I^2) * R_loss, where R_loss is the resistance causing the power loss.
• To minimize power loss in a circuit, it is important to use wires and components with low resistance.
• Power loss is dissipated as heat and can cause inefficiency in electrical devices.
• Transformers are used to step-up or step-down the potential difference in order to reduce power loss over long-distance transmission lines.

Electrical Energy and Power - Power loss (Continued)

• Power loss can be reduced by using thicker wires with lower resistance.
• Power loss is proportional to the square of the current, so reducing current can significantly decrease power loss.
• Power loss in transmission lines can be reduced by increasing the potential difference, which decreases the current for the same power transfer.
• Power loss is an important consideration in electrical systems as it affects the efficiency and cost-effectiveness of the system.
• Efficient power transmission and distribution systems play a crucial role in providing electricity to consumers effectively and economically.

Electrical Energy and Power - Electromotive force

• Definition: The electromotive force (emf) of a device is the work done per unit charge in moving a charge around a complete circuit.
• Symbol: emf (ε)
• Unit: volt (V)
• The emf of a cell or a battery is the energy supplied by the cell or battery per unit charge delivered to the external circuit.
• The emf of a device is typically greater than the potential difference across the device when it is connected in a circuit.
• The potential difference across a device in a circuit is equal to the emf minus the potential drop across the internal resistance of the device.

Electrical Energy and Power - Internal resistance

• Definition: The internal resistance of a device is the resistance offered by the components inside the device to the flow of current.
• Symbol: r
• Unit: ohm (Ω)
• The internal resistance of a device is responsible for the potential drop across the device when current flows through it.
• The internal resistance of a device is constant for a given device and is determined by the materials and construction of the device.
• When the internal resistance of a device is high, the potential difference across the device decreases, resulting in reduced current flow.

Electrical Energy and Power - Power in circuits

• The power (P) in an electrical circuit is the rate of energy transfer or the rate at which work is done.
• Power is equal to the product of the potential difference (V) across the device and the current (I) flowing through it.
• Formula: P = V * I
• Unit: watt (W)
• The power dissipated by a device can be calculated using the formula: P = I^2 * R, where R is the resistance of the device.
• In a series circuit, the total power supplied by the source is equal to the sum of the power dissipated by all the devices in the circuit.

Electrical Energy and Power - Power in circuits (Continued)

• In a parallel circuit, the total power supplied by the source is equal to the sum of the power supplied to all the devices in the circuit.
• Power can also be calculated using the formula: P = (I^2) * r, where r is the internal resistance of the device.
• The power delivered to the load is maximum when the internal resistance of the source is equal to the resistance of the load.
• The power delivered to a device can be controlled by either adjusting the potential difference or the resistance in the circuit.
• High power devices such as heaters and motors have low resistance and require higher potential difference to operate.

Electrical Energy and Power - Energy transfer in circuits

• Electrical energy (E) is the product of power (P) and time (t).
• Formula: E = P * t
• Unit: joule (J)
• The total electrical energy transferred in a circuit is equal to the product of the power and the time for which the device is connected to the circuit.
• Energy is not consumed or destroyed in a circuit, but rather is transferred and transformed into other forms such as heat, light, or mechanical work.

Electrical Energy and Power - Energy transfer in circuits (Continued)

• The electrical energy transferred to a device can also be calculated using the formula: E = V * Q, where Q is the charge that passes through the device.
• The unit of electrical energy, joule (J), is equivalent to one watt-second (W·s).
• One kilowatt-hour (kWh) is equal to 3.6 million joules (3.6 MJ) and is commonly used as a unit of electrical energy.
• To calculate the cost of electrical energy consumed, the number of kilowatt-hours used is multiplied by the cost per kilowatt-hour.
• It is important to conserve electrical energy and make efficient use of devices to reduce the consumption and cost of energy.

Electrical Energy and Power - Power loss

• In a circuit, power loss occurs due to resistance in the wires and components.
• The power loss can be calculated using the formula: P_loss = (I^2) * R_loss, where R_loss is the resistance causing the power loss.
• To minimize power loss in a circuit, it is important to use wires and components with low resistance.
• Power loss is dissipated as heat and can cause inefficiency in electrical devices.
• Transformers are used to step-up or step-down the potential difference in order to reduce power loss over long-distance transmission lines.

Electrical Energy and Power - Power loss (Continued)

• Power loss can be reduced by using thicker wires with lower resistance.
• Power loss is proportional to the square of the current, so reducing current can significantly decrease power loss.
• Power loss in transmission lines can be reduced by increasing the potential difference, which decreases the current for the same power transfer.
• Power loss is an important consideration in electrical systems as it affects the efficiency and cost-effectiveness of the system.
• Efficient power transmission and distribution systems play a crucial role in providing electricity to consumers effectively and economically.