what is the relationship between potential difference and direction of flow corrent in an electric circuit ?

Potential difference (U) measured in volts 
Current intensity (I) measure in amps 

 The higher the resistance, the greater the potential difference across the resistor. 

The I-V characteristics of a resistor are described by "ohms law". Ohms law states that the voltage across a resistor is proportional to the current through it. This is infact how "resistance" can be defined, as the ratio of proportionality between voltage and current:

i.e. V = IR

From the equation you can see that the voltage (potential difference) across the resistor increases as the value of R (resistanc) increases