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ScientificConstants

  

ModifyConstant

  

modify a physical constant definition

 

Calling Sequence

Parameters

Description

Examples

Calling Sequence

ModifyConstant( descriptor, value_eqn, opts )

ModifyConstant( descriptor, derive_eqn, derive_opts )

Parameters

descriptor

-

name; full name or symbol of physical constant

value_eqn

-

equation of the form 'value'=value_obj that redefines the value of the physical constant; value_obj must be of type constant or contain a Constant() object such that it evaluates to type constant

opts

-

equation(s) of the form option=value, where option is one of 'check', 'symbol', 'uncertainty', or 'units'; specify the nonderived physical constant definition

derive_eqn

-

equation of the form 'derive'=derive_obj that redefines the physical constant; derive_obj must be of type algebraic and contain at least one symbol or name of a physical constant

opts

-

equation(s) of the form option=value, where option is one of 'check' or 'symbol'; specify the derived physical constant definition

Description

• 

The ModifyConstant( descriptor, value_eqn, opts ) command modifies the definition of a derived or nonderived physical constant in the ScientificConstants package producing a nonderived constant for the current session.

• 

The ModifyConstant( descriptor, derive_eqn, derive_opts ) command modifies the definition of a derived or nonderived physical constant in the ScientificConstants package producing a derived constant for the current session.

• 

To update a constant for all future Maple sessions, add the ModifyConstant command to your Maple initialization file. For more information, see Create Maple Initialization File.

• 

In the derive_eqn equation of the form 'derive'=derive_obj, the derive_obj expression is typically a product of rational powers of numerics, Maple constants, and physical constant identifiers (for example, symbols). Exceptions are the abs function, and a sum with dimensionally consistent summands.

• 

The derive_opts and opts arguments can contain one or more of the following equations that set the physical constant definition.

  

 

  

'check' = true or false

  

When 'check'=true, ModifyConstant checks whether the given symbol matches the name or symbol of a physical constant in the package. If it does, an error is returned.  The default value of 'check' is true.  When 'check'=false, ModifyConstant attempts to remove from the package any conflicting physical constant.  This is unsuccessful if any conflicting constant is currently used in the definition of any derived physical constants.

  

 

  

'symbol' = symbol

  

This option defines the symbol of the physical constant. It cannot match the name or symbol of a physical constant in the ScientificConstants package (unless the 'check=false' option is given, see below). If the 'symbol' is modified, the descriptor must be the full name of the physical constant.

  

 

• 

The opts argument can also contain one or more of the following equations that set the nonderived physical constant definition.

  

 

  

'uncertainty' = uncertainty_obj

  

This option redefines the precision to which the physical constant's value is known.

  

If the pre-existing value of the 'uncertainty' is not undefined, this equation is required.

  

If the constant was previously defined as a derived constant, this equation is not required. The default value of the uncertainty is undefined.

  

The uncertainty_obj option must be of type constant (or be so after Constant() objects evaluate) or a list of the form uncer,uncertainty_opt where uncertainty_opt is 'relative' or 'uld' and uncer is of type constant (or is after Constant() objects evaluate).

  

If no uncertainty option uncertainty_opt is included, the value represents the absolute uncertainty of the physical constant. That is, the value is measured in units determined by the 'units' option.

  

If uncertainty_obj is of the form uncer,'relative', uncer is the relative uncertainty in the physical constant's value.  The quantity uncer*value_obj is the absolute uncertainty of the physical constant.

  

If uncertainty_obj is of the form uncer,'uld', uncer is the uncertainty in "units in the least digit" in the physical constant's value.  The quantity uncerSFloatExponentvalue_obj is the absolute uncertainty of the physical constant.  This form of uncertainty cannot be used with a non-float value_obj.

  

 

  

'units' = units_obj

  

This option redefines the units in which the value and uncertainty are measured. The units_obj option can be an expression that Units[Unit] interprets as a unit or a Unit() standard form. For more information, see Units.

  

This equation is optional.

Examples

withScientificConstants:

GetConstantc

speed_of_light_in_vacuum,symbol=c,value=299792458,uncertainty=0,units=ms

(1)

ModifyConstantspeed_of_light_in_vacuum,symbol=c0

GetConstantc0

speed_of_light_in_vacuum,symbol=c0,value=299792458,uncertainty=0,units=ms

(2)

AddConstantHooke1,symbol=k1,value=2.3,units=Nm

GetConstantk1

Hooke1,symbol=k1,value=2.3,uncertainty=undefined,units=Nm

(3)

ModifyConstantk1,value=2.3,units=Nm,uncertainty=0.1,relative

GetConstantk1

Hooke1,symbol=k1,value=2.3,uncertainty=0.23,units=Nm

(4)

AddConstantmass_ratio,symbol=`m[e]/m[p]`,derive=memp

evalfConstant`m[e]/m[p]`

0.0005446170233

(5)

ModifyConstantmass_ratio,symbol=`m[p]/m[e]`,derive=mpme

evalfConstant`m[p]/m[e]`

1836.152667

(6)

See Also

Create Maple Initialization File

Details of Commands for Physical Constants

Initial Physical Constants

ScientificConstants

ScientificConstants[AddConstant]

ScientificConstants[Constant]

ScientificConstants[GetConstant]

ScientificConstants[HasConstant]

Units

Units[Unit]

 


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