## Power Supply Internal Resistance Calculator

**Internal Resistance (R):** Ohms

Certainly, here’s a table listing the internal resistance of common types of power supplies:

Type of Power Supply | Typical Internal Resistance (Estimation) |
---|---|

Alkaline Battery (AA) | 150 – 300 milliohms (0.15 – 0.3 ohms) |

Lithium-Ion Battery | 30 – 100 milliohms (0.03 – 0.1 ohms) |

Lead-Acid Battery (12V) | 1 – 30 milliohms (0.001 – 0.03 ohms) |

NiMH Rechargeable Battery | 10 – 50 milliohms (0.01 – 0.05 ohms) |

Linear DC Power Supply | 1 – 10 ohms |

Switching DC Power Supply | 0.1 – 5 ohms |

Unregulated DC Adapter | 0.1 – 5 ohms |

Please note that these values are rough estimations and can vary significantly depending on factors such as the specific manufacturer, model, and condition of the power supply. Always refer to the manufacturer’s specifications for precise internal resistance values when available.

## FAQs

**How do you calculate internal resistance of a power supply?** The internal resistance (r) of a power supply can be estimated by measuring the voltage drop (ΔV) across the supply when a known current (I) is drawn from it and then using Ohm’s law: r = ΔV / I.

**What is the formula for internal resistance?** The formula for internal resistance (r) is r = ΔV / I, where ΔV is the voltage drop across the power supply, and I is the current drawn from it.

**How do you find the internal resistance of a source?** To find the internal resistance of a power source, you can connect a known resistor in series with the source, measure the voltage drop across the source when current flows through it, and then use Ohm’s law to calculate the internal resistance.

**What is internal resistance of a supply?** The internal resistance of a supply refers to the inherent resistance within the power supply itself, which causes a voltage drop when current is drawn from it. It can limit the supply’s ability to deliver current to a load.

**What is the typical internal resistance of a DC power supply?** The typical internal resistance of a DC power supply can vary widely depending on the type and quality of the supply. It can range from fractions of an ohm to several ohms.

**How do you check internal resistance with a multimeter?** To check the internal resistance of a power supply with a multimeter, set the multimeter to measure resistance (ohms), connect it to the power supply terminals, and measure the resistance. Keep in mind that this method provides an estimate and may not be highly accurate for very low resistance values.

**What is the formula for internal and external resistance?** The formula to calculate the total resistance (R_total) of a circuit with internal resistance (r) and external load resistance (R_load) in series is: R_total = r + R_load.

**What is internal resistance, and how can it be measured?** Internal resistance is the inherent resistance within a power source (e.g., a battery or power supply). It can be measured by applying a known load and measuring the voltage drop and current, then using Ohm’s law to calculate the internal resistance.

**What is an acceptable battery internal resistance?** Acceptable battery internal resistance depends on the application. For most consumer batteries, a low internal resistance is preferred because it allows for higher current delivery. However, specific values can vary widely.

**Does a power supply have internal resistance?** Yes, most power supplies have internal resistance, which can limit their ability to deliver current to a load efficiently.

**Do all electrical sources have internal resistance?** Most electrical sources, such as batteries and power supplies, have some level of internal resistance. However, the magnitude of this resistance varies between different sources.

**What is the internal resistance of a good voltage source?** A good voltage source typically has low internal resistance to minimize voltage drop when delivering current.

**Should a high voltage supply have high internal resistance?** No, a high voltage supply should ideally have low internal resistance to deliver high currents without significant voltage drops.

**Should a low voltage supply have low internal resistance?** Yes, a low voltage supply is generally designed to have low internal resistance to deliver current efficiently and maintain voltage stability.

**Does internal resistance affect voltage?** Yes, internal resistance affects the voltage output of a power source. When current flows through the internal resistance, it causes a voltage drop, reducing the effective output voltage.

**What is the typical internal resistance of a multimeter?** The internal resistance of a multimeter is usually very high, often in the range of megaohms (millions of ohms), to minimize interference with the circuit being measured.

**Can internal resistance be measured directly?** Internal resistance can be estimated indirectly by measuring voltage drop and current, but it cannot be measured directly as a separate component.

**Do digital multimeters have internal resistance?** Yes, digital multimeters have internal resistance, but it is typically very high and is considered negligible in most practical measurements.

**Does internal resistance change with current?** Internal resistance can vary with temperature, state of charge, and age of the power source but may not change significantly with current over typical operating ranges.

**What is the difference between resistance and internal resistance?** Resistance refers to the opposition to the flow of electric current in a circuit and is typically associated with external components like resistors. Internal resistance specifically refers to the inherent resistance within a power source or supply.

**Why is it important to know the internal resistance of a battery?** Knowing the internal resistance of a battery is important because it affects the battery’s ability to deliver current and maintain voltage under load. It can impact the performance and lifespan of the battery in various applications.

**What is the internal resistance of a 9V battery?** The internal resistance of a 9V battery can vary but is typically in the range of 1 to 5 ohms, depending on the brand and type of battery.

**What is the internal resistance of a 12V AGM battery?** The internal resistance of a 12V AGM (Absorbent Glass Mat) battery can range from 5 to 15 milliohms (0.005 to 0.015 ohms).

**What is the internal resistance of a 12-volt battery?** The internal resistance of a 12-volt battery can vary widely depending on the battery’s chemistry and quality, but it typically falls in the range of 1 to 100 milliohms.

**What is the internal resistance of a 12V lead-acid battery?** The internal resistance of a 12V lead-acid battery can range from 1 to 30 milliohms, depending on factors like size and condition.

**Does internal resistance cause voltage drop?** Yes, internal resistance causes a voltage drop in a power source when current is drawn from it. The higher the internal resistance, the greater the voltage drop.

**How does internal resistance affect power?** Internal resistance affects the power delivered by a source because it causes a voltage drop when current flows through it. This voltage drop reduces the available power to the load.

**What is the internal resistance of a power pack?** The internal resistance of a power pack or portable battery pack can vary widely based on its design and quality but is typically in the range of 10 to 100 milliohms.

**Do some electrical sources have no internal resistance?** In theory, all electrical sources have some level of internal resistance. However, ideal voltage sources are often modeled with zero internal resistance for simplification in circuit analysis.

**What happens when internal resistance is zero?** When internal resistance is zero, a power source is considered ideal. In practice, this means it can deliver current without any voltage drop due to internal resistance.

**What is the ideal internal resistance of a voltmeter?** The ideal internal resistance of a voltmeter is infinite (open circuit), meaning it should draw zero current from the circuit being measured to avoid affecting the voltage reading.

**What happens to an integrated circuit (IC) if the supply voltage is low?** If the supply voltage to an integrated circuit (IC) is too low, the IC may not operate correctly, and its functionality may be impaired. It can lead to errors, instability, or even complete failure.

**What happens if the power supply voltage is too low?** If the power supply voltage is too low, electrical devices connected to it may not operate properly, and their performance may be compromised. In extreme cases, they may not function at all.

**Is low internal resistance good?** Low internal resistance is generally considered good in power sources because it allows for efficient delivery of current without significant voltage drop.

**What happens if the supply voltage is too high?** If the supply voltage is too high, it can damage or destroy electrical devices connected to it. It can cause overheating, component failure, or even electrical fires.

**What is an example of internal resistance?** An example of internal resistance is the resistance within a battery that causes a voltage drop when it delivers current to a load.

**What affects internal resistance?** Several factors can affect the internal resistance of a power source, including temperature, state of charge, age, and the specific chemistry of the source.

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