# Formula Symbols - I

Written by Jerry Ratzlaff on . Posted in Nomenclature & Symbols for Engineering, Mathematics, and Science

## Formula Symbols

• See A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z

## I

SymbolGreek SymbolDefinitionUSMetricValue
$$R$$ - ideal gas constant constant constant $$0.082\;06\;L\;atm\;mol^{-1}\;K^{-1}$$
$$lx$$ - illuminance - $$lm\;/\;m^2$$  -
$$b$$ - impact parameter - -  -
$$Z$$ - impedance - -  -
$$Z_o$$ - impedance of vacuum constant constant $$376.730\;313\;461...\;kg\;m^2\;s^{-3}\;A^{-2}$$
$$d$$, $$\;d_i$$ - impeller diameter $$in$$ $$mm$$  -
$$I$$ - impulse $$lbf-sec$$ $$N-s$$  -
$$I$$ - incident energy $$Btu \;/\; ft^2-hr$$ $$W \;/\; m^2$$  -
$$H$$, $$\;L$$ - inductance - $$Wb\;/\;A$$  -
$$n$$ - index of refraction - -  -
$$X_L$$ - inductive reactance - -  -
$$a_i$$ - initial acceleration $$ft\;/\;sec^2$$ $$m\;/\;s^2$$  -
$$\omega_i$$ omega initial angular velocity $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$l_i$$ - initial length $$in \;or\; ft$$ $$mm \;or\; m$$  -
$$x_i$$ - initial position - -  -
$$T_i$$ - initial temperature $$^\circ F$$ $$C$$  -
$$t_i$$ - initial time $$sec$$ $$s$$  -
$$v_i$$ - initial velocity $$ft\;/\;sec$$ $$m\;/\;s$$  -
$$V_i$$ - initial volume $$in^3 \;or\; ft^3$$ $$mm^3 \;or\; m^3$$  -
$$p_i$$ - inlet pressure $$lb\;/\;ft^2 \;or\; psi$$ $$Pa$$  -
$$E_i$$ - input energy $$ft\;-\;lbf$$ $$J$$  -
$$W_i$$ - input work $$ft\;-\;lbf$$ $$J$$  -
$$ID$$ - inside diameter $$in$$ $$mm$$  -
$$ID$$ - inside diameter of pipe $$in$$ $$mm$$ -
$$D_b$$ - inside diameter of valve body outlet $$in$$ $$mm$$  -
$$D_p$$ - inside diameter of outlet pipe $$in$$ $$mm$$  -
$$a_i$$ - instantaneous acceleration $$ft\;/\;sec^2$$ $$m\;/\;s^2$$  -
$$\alpha_i$$ alpha instantaneous angular acceleration $$lbf\;/\;ft^2-sec$$ $$Pa-s$$  -
$$v_i$$ - instantaneous velocity - -  -
$$n_i$$ - instrinsic number density - -  -
$$I$$ - interference - -  -
$$a$$ - interference factor - -  -
$$alpha$$ alpha internal conversion coefficient - -  -
$$U$$ - internal energy $$ft-lbf$$ $$J$$  -
$$e$$ - internal roughness - -  -
$$d$$ - internal pipe diameter $$in$$ $$mm$$  -
$$G_0^{-1}$$ - inverse conductance quantum constant constant $$1.290\;640\;372\;17\;x\;10^4\;kg\;m^2\;s^{-3}\;A^{-2}$$
$$\alpha^{-1}$$ alpha inverse fine structure constant dimensionless constant dimensionless constant $$137.035\;999\;084$$
$$w_{ci}$$ - ion cyclotron circular frequency - -  -
$$T_i$$ - ion temperature - -  -
$$Ir$$, $$\;\xi$$ xi Iribarren number dimensionless dimensionless  -
$$\alpha$$ alpha isentropic compressibility $$1\;/\; R$$ $$1\;/\;K$$  -
$$k$$ - isentropic exponent - -  -
$$\beta$$ beta isobaric compressibility $$1\;/\; R$$ $$1\;/\;K$$  -
$$\kappa$$ kappa isothermal compressibility $$1\;/\; R$$ $$1\;/\;K$$  -
Symbol Greek Symbol Definition US Metric Value