Turning force

The turning force produced by two equal and opposite parallel forces acting on a body. Toxicity... 

The mechanism for 1,4-addition involves two stages (Following fig.). In the first stage, the nucleophile uses a lone pair of electrons to form a bond to the P-carbon. Simultaneously, the C=C ji bond breaks and both electrons are used to form a new ji bond to the carbonyl carbon. This in turn forces the carbonyl 7t bond to break with both of the electrons involved moving onto the oxygen as a third lone pair of electrons. The resulting intermediate is an enolate ion. Aqueous acid is now added to the reaction mixture. The carbonyl k bond is reformed, which forces open the C=C k bond. These electrons are now used to form a o bond to a proton at the a carbon. 

Eq. (8.31) to fonn Sx3 and E, n, a ) to form Sa2. The resultant Ss3Sa2 has the form of Eq. (8.32) with tif1> and associated with the symmetric and antisymmetric continuum wave functions, respectively. Consider now the effect of summing over m. Standard formulas [273, 281] imply that this summation introduces a Si 0, which, in turn, forces k = X via the first and second 3/ symbol in Eq. (8.32). However, it is possible to show that /-matrix elements associated with symmetric continuum eigenfunctions and those associated with antisymmetric continuum eigenfunctions must have k of different parities. Hence summing over m eliminates all contributions to Eq. (8.13) that involve both E n, a ) and E, n, s ). Thus, we find after m summation ... 

If a body with angular momentum L is subjected to a force F perpendicular to it, then it experiences a torque or turning force T ... 

If, instead of a straight wire segment, a current-carrying loop is placed in the magnetic field, a torque (turning force) is exerted on the loop. The torque, t, is given by ... 

Figure 17.5d illustrates pressure control by a hot vapor b3q)ass. The condenser is located below the liquid level in the drum (which may be horizontal or vertical). The condensate must be subcooled so that liquid surfaces in the drum are cooler than in the condenser. This causes a difference in vapor pressure large enough to transport condensate from the condenser into the drum. When column pressure rises, the pressure controller closes the valve. This reduces condensation at the drum surface and lowers the drum smTace temperatm e, and, therefore, the drum vapor pressure. This enhances the vapor pressure difference between the condenser and the drum, which in turn forces more liquid out of the condenser and into the drum. This exposes additional condensing surface in the condenser and increases condensation rate. 

Bolt torque The turning force in foot-pounds applied to a roof bolt to achieve an installed tension. 

This formula can perhaps better be understood by referring to Fig. 2.3. A small effort at a long distance from the fulcrum can balance a large load at a short distance from the fulcrum. Thus a turning force or turning moment depends upon the distance from the fulcrum and the magnitude of the force. 

The turning force or torque experienced by the rotor is produced by inducing an e.m.f. into the rotor conductors due to the relative motion between the conductors and the rotating field. The torque produces rotation in the same direction as the rotating magnetic field. 

Figure 2.49 Segment taken out of an induotion motor to show turning force (a) eonstruetion of an induotion motor, and (b) produotion of torgue by magnetio fields...

A cage rotor is used on single-phase a.c. motors, the turning force being produced in the way described previously for three-phase induction motors and shown in Fig. 2.49. Because both windings carry currents which are out of phase with each other, the motor is known as a split-phase motor. The phase... 

When the motor is first switched on, the centrifugai switch is closed and the magnetic fields from the two coils produce the turning force required to run the rotor up to full speed. When the motor reaches about 80% of full speed, the centrifugal switch clicks open and the machine continues to run on the magnetic flux created by the run winding only. 

Briefly describe what we mean by a turning force and give five practical examples of this effect. 

Use a sketch with notes of explanation to show how a turning force is applied to the rotor and, therefore, the drive shaft of an electric motor. 

The torque screwdriver is becoming increasingly popular in the electrical industry. A torque screwdriver is a screwdriver with an in-built mechanism to ensure that the screw can be tightened to a specified, pre-set torque or turning force. This ensures that tightening is sufficient to make a safe electrical connection, but not so excessive as to cause damage. 

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