# Why do we calculate EM ratio?

A magnetic field produced by Helmholz coils is used to deflect electrons into circular paths whose radii are known. By knowing the energy of the electrons and the magnetic field strength, the ratio of the charge to mass (e/m) of the electron is determined.

Introduction. In this experiment you will measure e/m, the ratio of the charge of an electron to the mass of an electron. The currently accepted value for e/m is 1.758820 × 1011 C/kg. The force will cause the electron to move in a circular orbit with radius r (uniform circular motion).

Furthermore, who gave the value of e m? Thomson was able to determine the charge-to-mass ratio of the electron. Today, the accepted value of is 1.7588196 10 C kg . The mass-to-charge ratio (m/Q) is a physical quantity that is most widely used in the electrodynamics of charged particles, e.g. in electron optics and ion optics.

People also ask, why is e M ratio important?

The measurement of e/m for electrons and protons was very important for determining the mass of the electron and proton (and other charged particles). But in order to get the mass, the charge had to be determined. So this is why Milliken’s oil drop experiment (1913) was also so important.

How was the charge to mass ratio of the electron determined?

The electron charge-to-mass ratio was measured by accelerating the electrons through a voltage Vx towards a positively charged plate. Some of the electrons pass through a small hole in the plate and form and electron beam that travels to a region where an electric field and a magnetic field was present.

### Which has the highest E M ratio?

The highest value of e/m ratio is . In ion, the charge is 2 (e) and mass is 4(m) hence . For H atom the charge is 0 so e/m ratio will be 0 whereas for ; the value of e is 1 and mass is also 1. Hence the e/m ratio for ion must be whereas for ion, it is .

### What is the value of electron?

Since the value of the elementary charge is roughly 1.602 x 10-19 coulombs (C), then the charge of the electron is -1.602 x 10-19 C. When expressed in atomic units, the elementary charge takes the value of unity; i.e., e = 1. Thus, the electron’s charge can be denoted by -e.

### What is Thomson method?

Thomson’s method – Determination of specific charge (e/m) of an electron. In 1887, J.J. Thomson, measured the specific charge (e/m) of the cathode ray particles. The specific charge is defined as the charge per unit mass of the particle.

### What is Q m?

Charge-to-Mass Ratio (Q/m). Charge density expressed per unit mass of condensed phase material. Also known as specific charge.

Rutherford

### What is helical method?

Abstract. In the helical method a cathode-ray tube is inserted in a solenoid and e/m determined from the condition for focusing deflected electrons to a spot on the screen.

### Why E M ratio of cathode rays is constant?

Cathode rays are beam of electrons which are negatively charged. These electrons are identical. Hence, the charge to mass ratio (e/m) of cathode rays is same for all the gases.

### Do electrons have mass?

Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton.

### What is meant by e M ratio?

Objective To measure the electronic charge-to-mass ratio e/m, by injecting electrons into a magnetic field and examining their trajectories. The experiment involves injecting electrons into a magnetic field that is gen- erated by Helmholtz coils.

### What is the accepted value for E m?

The accepted value of e/m is 1.76 x 1011 C/kg. You will do well to get a result that is the correct order of magnitude. There are quite large uncertainties in the radius measurements and some uncertainty in the measurement of the magnetic field strength.

### How do you define charge?

In physics, charge, also known as electric charge, electrical charge, or electrostatic charge and symbolized q, is a characteristic of a unit of matter that expresses the extent to which it has more or fewer electrons than protons.

### Who discovered electrons?

Electron was discovered by J. J. Thomson in 1897 when he was studying the properties of cathode ray.

### Why is Em ratio of electron constant?

Here m is the mass of the particle of cathode rays in kg and e is it’s charge in coloumb(C). The particles are negatively charged and therefore the charge on the cathode ray particle which was later named as electron is represented as −e. The value of e/m remained constant irrespective of the nature of the gas.

### What is the charge and mass of a proton?

Protons are found in the nucleus of every atom but can also be found away from the nucleus, most commonly as ionized hydrogen. A proton has a charge of +1, or 1e, which is equal to 1.602 x 10^-19 coulombs, and a mass of 1.67 x 10^-27 kg.