# Sources of error in emf and internal resistance experiment

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The electromotive force (**EMF**) of a **source**, is a measure of the energy the **source** gives to each coulomb of charge. The **EMF** is measured in volts ( V ). At first sight, the name **EMF** implies that it is a force that causes the current to flow but this not correct, because it is not a force but energy supplied to the charge by some **source** of energy. Part 1: Setting up your circuit. Using the PHET Circuit Construction kit, use a battery, resistor, ammeter, and voltmeter to build the circuit design shown in the schematic diagram on the right. . On the right of the simulation window there is a dropdown menu for “Battery **Resistance**”. Choose an **internal resistance** and circle your selection.

Answer (1 of 6): For circuit analysis problems in electrical engineering and physics, the **sources** are typically considered as ‘ideal’ where they have no **internal** resistances. For real **sources** of **EMF** like batteries, generators, induced voltage in windings and conductors, etc. the **internal** resistan. The dry cells **EMF** together with its **internal** **resistance** can alternatively be calculated by other methods. A plot of terminal voltage versus current can help achieve the above. V varies inversely with changes in I to produce a straight line graph. The line equation of y=mx+c, is applicable to the formula of electromotive force, E= Ir.

The **internal** **resistance** **of** a **source** **of** **e.m.f**. has two effects: It results in a voltage across the terminals of the **source** dropping as a current is drawn from it. It results in the **source** being less than 100% efficient as energy is dissipated in the **internal** **resistance** as current flows through it. Identify and construct an appropriate graph for the purpose of determination of **emf and internal resistance** of the dry cell. Determine the **emf and internal resistance** of the dry cell. 4 Summary of Theory. A constant current can be maintained in a closed circuit through a **source** of energy, an **emf**, from the term electromotive force. Question 1: The terminal voltage of a cell in an open circuit condition is. Less than its **emf**. More than its **emf**. Equal to its **emf**. Depends on its **internal resistance**. Solution: Option C. Equal to its **emf**. The terminal voltage of a cell in open circuit condition will be equal to the **emf** of the cell as the circuit is open there won’t be any.

**Internal Resistance**. * Abstract. This **experiment** was performed so as to investigate the concept of **internal resistance** which is an inherent **resistance** present in all electrical devices and is mainly ignored in most of the circuit analysis. The objective of the analysis was achieved by first connecting two 100 k Ohms resistors to a 10 V power.

Answer to 3. Find the **emf** **and** **internal** **resistance** **of** the. the current intensity for each **resistance** (R1, R2, R3). Record the table. Plot a graph of V against I. This is the current-voltage characteristics of the cell. The characteristics is shown as straight line in Figure 2. Figure 2 To derive the equation relating **EMF**, terminal PD, current and **internal** **resistance** use.

Episode 121-3: **Internal resistance** of a C cell (Word, 28 KB) To determine E and r from the **experimental** results, there are various approaches. The simplest is to measure terminal voltage ( V) and current ( I) and to plot V against I. This gives an intercept at V. The negative intercept on the y-axis is the **internal** **resistance**. Theory: The **emf** **of** a cell is the total p.d. it can produce around the circuit, including any potential wasted in driving current through the cell itself. The **internal** **resistance** **of** a cell is simply the **resistance** from one terminal of the cell to the other. since . V = IR. then . E. Firstly, when explaining to students, students should be made clear how the systematic **errors** **of** the **experiment** are produced: because the ammeter has **internal** **resistance**, the result of voltage dividing makes the reading of the voltmeter smaller than the real value of the circuit voltage, so the circuit voltage should be corrected.

ε = IR + Ir. = V + Ir. V = ε – Ir. So V = ε – Ir, where V is the potential difference across the circuit, ε is the **emf**, I is the current flowing through the circuit, r is **internal resistance**. Usually, the **internal resistance** of a cell is not considered because ε >> Ir. The value of **internal resistance** changes from cell to cell.

the diagram. The **resistance** of Q is greater than the **resistance** of R. Which statement concerning the readings on the voltmeters is true? A. V 1 + V 2 + V 2 = **emf** B. V 3 > V 2 C. V 2 > V 3 D. V 1 > V 2 + V 3 Question 5 Three ohmic resistors of **resistance** R, 2R and 4R are connected in series to a voltage **source** having an **emf** of V and an **internal**. Users of laboratory standard platinum **resistance** thermometers need take more care to eliminate self heating **errors**. DC **Errors** Small D.C. voltages may be generated in p.r.t.’s due to thermoelectric effects caused by the joining of dissimilar metals in the construction of the p.r.t.

A **source** of **e.m.f**. always has some **resistance** to electric current within it, called its **internal resistance**. The **internal resistance** of a **source** of **e.m.f**. has two effects: It results in a voltage across the terminals of the **source** dropping as a current is drawn from it. It results in the **source** being less than 100% efficient as energy is.

Identify and construct an appropriate graph for the purpose of determination of **emf and internal resistance** of the dry cell. Determine the **emf and internal resistance** of the dry cell. 4 Summary of Theory. A constant current can be maintained in a closed circuit through a **source** of energy, an **emf**, from the term electromotive force. The two 1.5 V cells provide an **emf** of 3 V in series. If the current flowing is 0.5 A as stated, then for the potential difference across the **internal resistance** to be 0.5 V (that is, 3 V–2.5 V) the **internal resistance** of the cells combined would need to be 1Ω. The cells are in series so the **resistance** of each is 0.5 Ω. • 2.

The dry cells **EMF** together with its **internal** **resistance** can alternatively be calculated by other methods. A plot of terminal voltage versus current can help achieve the above. V varies inversely with changes in I to produce a straight line graph. The line equation of y=mx+c, is applicable to the formula of electromotive force, E= Ir.

**EXPERIMENT** 11 THE **POTENTIOMETER** I. THEORY The purpose of this **experiment** is to measure the electromotive force (**emf**) **and internal resistance** of a dry cell. The terminal voltage of a cell is the potential difference between its terminals. The **emf** of a cell may be defined as the terminal voltage of the cell when not under load, that is,. The **Internal Resistance** of the battery is 12.237 Ohms. This is indeed much smaller than the **resistance** we used. 2. The **EMF** is greater than the terminal voltage (rating) of the battery. The obtained electromagnetic force being 6.495V and the given battery voltage rated at 6 Volts. We speculate that the 6Volts on the battery is a rounded figure. **EXPERIMENT** 11 THE **POTENTIOMETER** I. THEORY The purpose of this **experiment** is to measure the electromotive force (**emf**) **and internal resistance** of a dry cell. The terminal voltage of a cell is the potential difference between its terminals. The **emf** of a cell may be defined as the terminal voltage of the cell when not under load, that is,. 1. **Internal Resistance** in Series Circuits In this lesson we will look at the concept of **resistance and internal** cell **resistance**, and then do calculations with a circuit that contains resistors in series. 2. Parallel Circuits In this lesson resistors in parallel are investigated, and problems in which a circuit that.

Objectives: The objectives of this **experiment** is to determines the **emf** ɛ and **internal resistance** r of new and old dry cells using the graph of the terminal voltage V T across the cells versus the current I that is supplied by the cell. Then we will compare the measured and calculated results for the two cells. Theory: The theory behind this lab is that any device that converts other forms. The Electromotive Force or **EMF** is the total energy transferred into electrical energy per unit charge by a voltage generator such as a battery or electrical generator.. It is given the symbol ε - this is the Greek letter 'epsilon'. So, by definition: ε = W/Q. where. W = total energy transferred. Q = unit charge. It is basically the potential difference across a cell, or other power suppl,y.

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**In** case of Ohm's law, you can commit a personal **error** by: Wrong connecting the circuit The ammeter is used to measure the current. It always connects in series with the circuit. Wrong connecting the ammeter will damage the instrument. The voltmeter measures the potential difference between two points. It connects in parallel to the circuit. **In** case of Ohm's law, you can commit a personal **error** by: Wrong connecting the circuit The ammeter is used to measure the current. It always connects in series with the circuit. Wrong connecting the ammeter will damage the instrument. The voltmeter measures the potential difference between two points. It connects in parallel to the circuit. Electrical **Sources** & **Internal Resistance**. STUDY. Flashcards. Learn. Write. Spell. Test. PLAY. Match. Gravity. Created by. chloeaplus. Terms in this set (14) what is electromotive force? (**EMF**) the voltage of a cell or battery. what is **internal resistance**? The **resistance** of a power supply.

. 27,376. 6,045. Hi. You have brought up two different issues. An **emf source** does not, by definition, have an **internal** resistor. A real **source** of **emf**, if it is located in a specific place, (often) has an equivalent circuit of a true **emf** in series with a series resistor. All the same rules apply to that resistor as the other resistors in the circuit. **In** case of Ohm's law, you can commit a personal **error** by: Wrong connecting the circuit The ammeter is used to measure the current. It always connects in series with the circuit. Wrong connecting the ammeter will damage the instrument. The voltmeter measures the potential difference between two points. It connects in parallel to the circuit. Identify and construct an appropriate graph for the purpose of determination of **emf** and **internal resistance** of the dry cell. Determine the **emf** and **internal resistance** of the dry cell. 4 Summary of Theory. A constant current can be maintained in a closed circuit through a **source** of energy, an **emf**, from the term electromotive force. The work on **EMF** and **internal resistance** draws on ideas about voltage, current and charge that were discussed in previous sections. The idea of **EMF** (electromotive force) has already been introduced but may well need reinforcement, along with the definition of the volt, and there is a lot to be gained by beginning this work with a general discussion of energy transfers within. Determine the **emf** **and** **internal** **resistance** **of** an electrical cell Practical activities have been safety checked but not trialled by CLEAPSS. Users may need to adapt the risk assessment information to local circumstances. Practical 3: Determine the **emf** **and** **internal** **resistance** **of** an electrical cell Objective Safety.

V load = I ⋅ R. Similarly, from Ohm's Law, the potential difference across the **internal resistance** is: V **internal resistance** = I ⋅ r. The potential difference V of the battery is related to its **emf** E **and internal resistance** r by: E = V + I r or V = E − I r. The battery is the **source** of energy and the energy provided per unit charge (**emf**.

This option allows users to search by Publication, Volume and Page Selecting this option will search the current publication in context. Book Search tips Selecting this option will search all publications across the Scitation platform Selecting this option will search all publications for the Publisher/Society in context. Solution. Verified by Toppr. 1. 1. The potential difference between the ends of the potentiometer wire or the **emf** of the cell connected in the main circuit may not be greater than the **emf** of the cells whose **emf** are to be compared . 2. 2. The positive terminals of the cells and the battery used in the circuit might not be connected to the same.

ε = IR + Ir. = V + Ir. V = ε – Ir. So V = ε – Ir, where V is the potential difference across the circuit, ε is the **emf**, I is the current flowing through the circuit, r is **internal resistance**. Usually, the **internal resistance** of a cell is not considered because ε >> Ir. The value of **internal resistance** changes from cell to cell. **Power and Internal Resistance**. Consider a simple circuit in which a battery of **emf and internal resistance** drives a current through an external resistor of **resistance** (see Fig. 17 ). The external resistor is usually referred to as the load resistor. It could stand for either an electric light, an electric heating element, or, maybe, an electric. 1. **Internal Resistance** in Series Circuits In this lesson we will look at the concept of **resistance and internal** cell **resistance**, and then do calculations with a circuit that contains resistors in series. 2. Parallel Circuits In this lesson resistors in parallel are investigated, and problems in which a circuit that.

Firsly what did I use for this work: battery, voltmeter, ammeter, toggle, connecting wires. 1. Measure electromotive force of power supply (a battery's in my case). 2. Mark ammeter's and voltmeter's results when a toggle is on. Calculate rap (there is a formula above). Calculate power supply's **resistance** and electromotive force absolute and. Magnetic Fields and Induced **EMF** Austin Glass 11/3/ ABSTRACT Electromotive Forces convert one form of energy to another. Varying the magnetic field or the size of loop can also cause changes in current. The two 1.5 V cells provide an **emf** of 3 V in series. If the current flowing is 0.5 A as stated, then for the potential difference across the **internal resistance** to be 0.5 V (that is, 3 V–2.5 V) the **internal resistance** of the cells combined would need to be 1Ω. The cells are in series so the **resistance** of each is 0.5 Ω. • 2.

Firstly, when explaining to students, students should be made clear how the systematic **errors** of the **experiment** are produced: because the ammeter has **internal resistance**, the result of voltage dividing makes the reading of the voltmeter smaller than the real value of the circuit voltage, so the circuit voltage should be corrected.

Answer: b) A lamp, rated at 30W, is connected to a 120V supply. i) Calculate the current in the lamp. Answer: ii) If the resistor in part (a) is replaced by the lamp described in part (b), determine how many cells, each of **emf** 1.5V **and internal resistance** 1.2, would have to be connected in series so that the lamp would operate and its proper.